PHP is a server-side scripting language that lets you generate dynamic HTML content. It has a C-like format with lots of inbuilt functions that make it specialised for such situations. Another such server-side scripting language is ASP which is developped and marketed by Microsoft for Windows. PHP on the otherhand is opensource and is cross-platform compatible (it will run on Windows, Linux, etc). PHP is available at
http://www.php.net
MySQL is a SQL Database software... SQL stands for Structured Query Language - it consists of a series of commands that all compatible software (such as MySQL, miniSQL, PostgreSQL) must contain... For instance, there are commands to retrieve data, filter it, sort it, add/delete data, etc. By making all the software retain the same commands and format, it is easier for programs from PHP, etc to migrate from one database server to another if the need arises. You can find MySQL at
http://www.mysql.com
Arun