No it is a complete operating system that can run alongside with XP (dual boot) or replace it. There are many different linux operating systems, called distro's or distributions, you should find one that does what you want. Popular ones are Fedora (former Red Hat), SuSE, Ubuntu, Debian (is for more experienced users).

Most linux distros include a large amount of software like browser, office suite, games, anything you need and more than you get with windows. Depending on the distro, installation can be a pain in the donkey or a breeze. Usually its really easy, you download it (legally, because its free) from a hyper fast FTP server, burn it to CD or DVD and boot with the disc in the drive. Then just follow the steps.

There's lots and lots of stuff you can do with Linux, anything you'll ever want is available for Linux and most often its free. Not everything is free though, SuSE for example isn't, and some software isn't free either such as ummm kBasic i think, but you don't need it and theres usually a free alternative.

Google for 'linux distro comparison', there must be tons of emAlso search on youtube for 'Beryl'. Stunning