Bittorrent is a file sharing method used by a growing number of people. It's main difference lies in it's sharing method. Instead of sharing one giant file such as a movie it shares packets, much as the web is designed to do. This file sharing method takes a file, for example one of the latest movies, splits it into hundreds of packets. As all these packets are made available one person may download a file from several locations.
Instead of getting one file from one person as you do with Kazaa and other programs you get the same file but fragments of it from hundreds of people. This increases the speed at which you may get files from one location to another.
It's strength and it's weakness is that it depends too much on other people as with all sharing programs. The advantage though is when downloading popular files. As this network deals with packets from various files rather than complete files sharing may be carried out much faster. Once you have downloaded a small 50 kilobyte segment it is made available for others to download. In so doing the network can expand to such an extent that it works better as more people are downloading.
Every person downloading the same file can download packets from each other reducing the stress on the one with the most packets. Imagine that you're sharing a book with several hundred pages. As some people have more pages from that book they are able to photocopy and pass on the page to another person and this continues. As more people have copies of the book they should be able to share a higher percentage of the file. This is a highly dynamic method for sharing files and will probably become the future of file sharing.
Azureus: Java Bittorrent client