No necessarily, PHP can be used on various other web servers, not just Apache, but Apache is the most popular. MySQL is a stand-alone database engine and is used by a lot of other stuff, not just PHP apps.
The best server yet for php serving is Apache, as PHP and Apache work closely together. The MySQL community database is a good server for PHP applications, this is why we talk about w/xamp servers, Windows/Linux Apache MySQL PHP servers.
WAMP is an abbreviation of "Windows, Apache, MySQL, and PHP", so it uses MySQL database server.
*AMP (<OS> Apache Mysql PHP) stacks are incredibly popular, supported, and documented, creating a great environment for a beginner, and very much stable enough for a senior engineer.
WAMP stands for Windows Apache Mysql PHP. Mysql is the default database in WAMP
LAMP stands for Linux-Apache-MySQL-PHP. In simpler terms it contains everything to build a php application on a linux platform.
Let me answer from less 'technicall' point of view. Apache is the HTTP server. It gets the HTTP requests and answers with the HTML code. PHP is used to generate this HTML dynamically on server side. MySQL is used by PHP for getting the data. Once the Apache HTTP server gets the request for the page with php (or php3, php4, phtml or whatever is configured in Apache's config file), it calls PHP interpreter to generate HTML. Then this HTML is returned to the client - internet browser which sent HTTP request. PHP has got an access to MySQL DB via several APIs. This simply means, that you can just call some function in PHP script to select, import update or delete some data in a table of DB. You can also maintain the DB, create, delete new tables a.s.o. There is a lot of functions for that ;)
The main causes of errors in PHP can be the problems occurring from the MYSQL database (if there) or errors from Apache handler. These errors can be prevented by hosting the MYSQL database on a trusted and good server.
facebook definatly runs on php (as you can tell by going to www.facebook.com/home.php). Also when you apply for a job to the company mysql knowledge is a must. However as for the platform it runs on that is difficult to say for sure, however i would imagine them to be using a classical LAMP setup (Linux Apache MySQL and PHP) as is very common with php/mySQL sites.
Ideal thing to do would be to delete all your installation & install a single WAMP/LAMP server. It combines all the features necessary to run php including windows/linux, apache, mysql & php
Xampp (X-os,apache mysql Php Perl) X-OS means in runs in all OS
Either you could download latest version of php, mysql & apache server or better you just need to install xampp. Versions of it are available for all OS
You can connect any DB via PHP if you have database specific database extensions defined. LAMPP stack refer to 'Linux Apache Mysql PHP Perl'. Hence this stack is famous for php development as it include all the needed components for web development. Mysql is preferred mostly because it's extension is added by default in XAMPP or WAMPP stack.