A package consisting of Apache, mySQL, PHP and Perl, available for multiple platforms meant for use by developers.
XAMPP is a package consisting of Apache, mySQL, PHP and Perl meant for software developing purposes. These are all distributed as one, making it easy for anyone to 'bootstrap' all the packages on a developers machine.
XAMPP packages are currently available for Windows, Linux, OS X and Solaris. For more information see the XAMPP web page at http://www.apachefriends.org/en/xampp.html
Questions about using XAMPP in a production environment are off-topic on Serverfault.
