Typo3 is available for download in multiple formats. First is the PHP source code of Typo3 and second form is complete installation package.

In case you already have Webserver, PHP, and Mysql setup ready and running you can use the source of Typo3 to get started (http://typo3.org/download/packages/). The Typo3 source is again divided in to types of formates :-

1. Zip files - This is for windows based Operating systems
2. Tar files - This is for Linux based Operating systems (includes symlinks).

For newbies in the world of Webservers and PHP the easiest way is the installer typo3.org/download/installers/ . The installer are available depending on Operating systems. The installer includes webserver, PHP, mysql setup necessary to run Typo3.