It is a program that you can download off of the internet. This program allows you to compress files so that the files are smaller to send online and do not take as long to send and recieve. Another good example of compression is DVD Players. DVD Players use a type of compression call mpeg2 witch is a type of digital compression. An mp3 is a wave file compressed into a mp3 file that is much smaller so that you can send them over the internet faster and easier.
Compression is here.
We went from LPs, to eight tracks, to cassettes, to Compact Discs, and now MP3s. The audio world is changing very rapidly. I think that it is for the better. We now have better quality and more convenient ways to store media. The storage is the exciting thing.