Here you have the list of available repositories. Not all repositories are available, according to which media you use for installing. The repositories selection determines which packages will be available for selection during the next steps.
The Core repository cannot be disabled as it contains the base of the distribution.
The Nonfree repository includes packages that are free-of-charge, i.e. Mageia may redistribute them, but they contain closed-source software (hence the name - Nonfree). For example this repository includes nVidia and ATI graphics card proprietary drivers, firmware for various WiFi cards, etc.
The Tainted repository includes packages released under a free license. The main criteria for placing packages in this repository is that they may infringe patents and copyright laws in some countries, e.g. Multimedia codecs needed to play various audio/video files; packages needed to play commercial video DVD, etc.
