Sharing music online: some musicians hate it, some musicians love it. It's barely legal. And millions of people do it every day.

It's called "Peer-to-Peer Sharing" (P2P). It works by having users voluntarily install special P2P software on their machines. Once the P2P software is in place, these users start to trade music MP3 files of their favorite songs. No charge, no cost...it's as easy as doing a Google search.

This file trading, called "uploading and downloading", is the heart of the P2P online community. Although these large 5 megabyte music files do eat up "bandwidth" (electronic capacity of Internet cables), people love their music, and millions of people trade MP3 files every day.

The most famous of P2P networks, "Napster 1.0", flourished from 1999 to 2002, and enjoyed 70 million users trading music. At its peak in 2002, Napster was estimated to have 85% of the college students in the USA participating in some way in online music trading.

Something sad happened to Napster in 2002: the Recording Industry Association of America sued Napster for copyright infringement, and ordered 250,000 songs removed from its P2P community.