When you find one that you don't know, they are very easy to google to a site that gives a great definition. wiki has a set of definitions, and a lot of other sites do too.
So for "mp3 file" I get, for instance: MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression. It is a common audio format for consumer audio storage, as well as a de facto standard of digital audio compression for the transfer and playback of music on digital audio players. MP3 is an audio-specific format that was designed by the Moving Picture Experts Group. The group was formed by several teams of engineers at Fraunhofer IIS in Erlangen, Germany, AT&T-Bell Labs in Murray Hill, NJ, USA, Thomson-Brandt, and CCETT as well as others. It was approved as an ISO/IEC standard in 1991.
Geek Speak » in reply to Pssssst
Just another silly industry acronym for a file type.