Web Development Glossary


(Apache Web Server, Apache HTTP Server)
The Apache HTTP Server is an open source software web server. Apache is run on Unix-like operating systems, and was developed for use on Linux.


(Application Programming Interface)
Defines how different software applications can communicate with each other. A software-to-software interface, not a user interface. A software company releases its API to the public so that other software developers can design products that are powered by its service.


(Command Line Interface)
A CLI is a type of human-computer interface (i.e., a way for humans to interact with computers) that relies solely on textual input and output.


(Domain Name Service)

DRY Principle

In software engineering Don’t Repeat Yourself (DRY) is a principle of software development aimed at reducing repetition of software patterns, replacing it with abstractions, or repetition of the same data, using data normalization to avoid redundancy.


  • In computer science falsy can mean “something that is equivalent to false”.
  • A falsy value is a value that translates to false when evaluated in a boolean context by a loosely-typed programming language. JavaScript and PHP both use type conversion to coerce any value into a boolean in contexts that require it, such as conditionals and loops.
  • falsy can also be spelled falsey.
  • The opposite of falsy is truthy.


Hostnames are human-readable labels that correspond to the network address of a computer connected to a network.


(HyperText Transfer Protocol)
The HyperText Transfer Protocol is the standard transmission protocol used on the World Wide Web. The Apache web server implements version 1.1 of the protocol, referred to as HTTP/1.1 and defined by RFC 2616.


The Internet is the name for the system by which independant nettworks can communicate with eachother
massive networking infrastructure which operates using the Internet Protocol (IP), a collection of .


(Internet Protocol)
IP is the communications protocol underlying the Internet. The Internet Protocol allows large, geographically diverse networks of computers to communicate with each other quickly and economically over a variety of physical links.

IP Address

(Internet Protocol Address)
An IP address is a numeric representation of a computer’s location on a network. IP addresses look something like Computers on the Internet use IP addresses to route traffic and establish connections among themselves but people generally use the human-friendly names made possible by the Domain Name System. IP addresses can be static or dynamic.


The central module of an operating system. It is the part of the operating system that loads first, and it remains in main memory. Because it stays in memory, it is important for the kernel to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. Typically, the kernel is responsible for memory management, process and task management, and disk management.

KISS principle

Keep it Simple Stupid is a design principle noted by Kelly Johnson, lead engineer on the Blackbird spy planes in 1960. The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore simplicity should be a key goal in design and unnecessary complexity should be avoided.


(Linux, Apache, MySQL and PHP)
LAMP is an open-source Web development platform, also called a Web stack, that uses Linux as the operating system, Apache as the Web server, MySQL as the RDBMS and PHP as the object-oriented scripting language. Perl or Python is often substituted for PHP.

The key to the idea behind LAMP, a term originally coined by Michael Kunze in the German magazine c’t in 1998, is the use of these items together. Although not actually designed to work together, these open source software alternatives are readily and freely available as each of the components in the LAMP stack is an example of Free or Open Source Software (FOSS).

LAMP has become a de facto development standard. Today, the products that make up the LAMP stack are included by default in nearly all Linux distributions, and together they make a powerful web application platform.

The original LAMP acronym has spawned a number of other, related acronyms that capitalize on the main focus of the original combination of technologies to provide feature rich Web sites. Some of these related Web stacks include LAPP, MAMP, and BAMP.


Open source computer operating system based on Unix. Mostly used on servers and web servers.

Pronounced lee-nucks or lih-nucks. A freely-distributable open source operating system that runs on a number of hardware platforms. The Linux kernel was developed mainly by Linus Torvalds and it is based on Unix. Because it’s free, and because it runs on many platforms, including PCs and Macintoshes, Linux has become an extremely popular alternative to proprietary operating systems.
Operating System (OS)
The operating system is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop — it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.


The underlying hardware or software for a system. For example, the platform might be an Intel 80486 processor running DOS Version 6.0. The platform could also be UNIX machines on an Ethernet network.
The platform defines a standard around which a system can be developed. Once the platform has been defined, software developers can produce appropriate software and managers can purchase appropriate hardware and applications. The term is often used as a synonym of operating system.

Proxy Server

Proxy servers sit between a client program (typically a Web browser) and an external server (typically another server on the Web) to filter requests, improve performance, and share connections.


(Server Application Programming Interface)
SAPI is the mechanism that controls the interaction between the “outside world” and the PHP engine. So, you would always want to use it. In fact, you cannot avoid using it without a lot of effort since even CLI is considered a SAPI.


(Web Server)
A server is a computer that delivers (serves) data. A web server is a computer that delivers data to the web over a network. A Web server needs an IP address and software like Apache to use HTTP to exchange data on a network. A server can also be called a host or a node.

SOLID Principles

In object-oriented computer programming, the term SOLID is a mnemonic acronym for five design principles intended to make software designs more understandable, flexible and maintainable:

  • Single Responsibility
    A class or a method should have only a single responsibility.
  • Open/closed
    Software entities should be open for extension, but closed for modification.
  • Liskov substitution
    Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.
  • Interface segregation
    Many client-specific interfaces are better than one general-purpose interface.
  • Dependency inversion
    One should depend upon abstractions, not concretions.


(Web Stack)
A collection of software usualy comprised of an operating system, web server, database server, and programming language. One of the most most popular web stacks is LAMP (Linux, Apache, MySQL, PhP).


  • In computer science truthy can mean “something that is equivalent to true”.
  • A truthy value is a value that translates to true when evaluated in a Boolean context by a loosely-typed programming language. JavaScript and PHP both use Type Conversion to coerce any value into a Boolean in contexts that require it, such as conditionals and loops.
  • The opposite of truthy is falsy.


Uniform Resource Identifier
A compact string of characters for identifying an abstract or physical resource. It is formally defined by RFC 2396. URIs used on the world-wide web are commonly referred to as url.
Virtual Host
Serving multiple websites using a single instance of Apache. IP virtual hosting differentiates between websites based on their IP address, while name-based virtual hosting uses only the name of the host and can therefore host many sites on the same IP address.
See: Apache Virtual Host documentation


(Uniform Resource Locator)
A URL is the global address of documents and other resources on the World Wide Web. URLs are used as links to other Web sites. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. A URL implies the means to access an indicated resource, which is not true of every URI. The term “Web address” is a synonym for a URL that uses the HTTP / HTTPS protocol.

The first part of a URL is called a scheme or protocol and it indicates what protocol to use. Examples are HTTP, HTTPS, and FTP.

The second part of a URL (everything after the ‘://’) is called a hostname or a resource name and is specified by the IP address or it’s domain name where the resource is located.

The third part of a URL (everything after the hostname) is called a path and is composed of segments separated by slashes.

The Uniform Resource Locator (URL) was developed by Tim Berners-Lee in 1994 and the Internet Engineering Task Force (IETF) URI working group. The URL format is specified in RFC 1738 Uniform Resource Locators (URL).

World Wide Web

The World Wide Web, or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet. The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. Web services, which use HTTP to allow applications to communicate in order to exchange business logic, use the the Web to share information. The Web also utilizes browsers, such as Internet Explorer or Firefox, to access Web documents called Web pages that are linked to each other via hyperlinks. Web documents also contain graphics, sounds, text and video.

The Web is just one of the ways that information can be disseminated over the Internet. The Internet, not the Web, is also used for e-mail, which relies on SMTP, Usenet news groups, instant messaging and FTP. So the Web is just a portion of the Internet, albeit a large portion, but the two terms are not synonymous and should not be confused.