MediaPlayers are applications that allow you to view various 'media'. Linux used to be slated for its lack of ability to play MultiMedia (music, video, etc). Today there is almost nothing that you can't play on Linux, and it's not very tricky at all. In fact you may find it to be much less of a hassle than the constant CoDec-hunting needed in MicrosoftWindows.
Quick summary of players avalible for Linux:
Many LinuxDistributions will not play MP3 or DVD by default due to patent issues. For DebianLinux see AptSourcesList for more details.
If you're a programmer, and you want to build media into your application, you could look at something like
10 pages link to MediaPlayer: