1. Introduction - What is LAMP?
LAMP = Linux, Apache, MySQL and Perl/PHP/Python
The point is a web and Internet configuration that is portable across all Unixes (and possibly even Windows) servers, composed entirely or almost entirely of open-source software, whose initial software costs can be zero.
This does not means setting it up and maintaining the site will not cost a thing. It will. But there is evidence that such configurations are generally more robust, configurable and less costy to maintain than the equivalent commercial ones.
There are many variations on this theme: