From LXF Wiki
LAMP stands for Linux, Apache, MySQL and Perl/Python/PHP. The "LAMP stack," as it is sometimes called, has become the de facto non-Microsoft standard architecture for hosting web applications and web services. Something like 40% of web services around the world are built on LAMP.
- Linux: the OS kernel we all love. Don't forget the Gnu, as in GNU/Linux. ("GAMP" anybody?)
- Apache: the world's most popular web server.
- MySQL: a relational database.
- Perl, Python and PHP: programming languages for writing the actual web applications. Ruby on Rails is another, and may be deemed to start with an honorary P.
All the basic LAMP software is available under free and open licenses. MySQL also offers a commercial closed-source license, allowing you to merge your own proprietary tweaks into their code.