If you've been wondering what really BitTorrent is, and how to use it, here's a quick and dirty guide I've drawn up -- with terms defined as simply as possible -- so you can start using BitTorrent at once:

1. Bittorrent is a peer-to-peer (P2P) protocol and software created by US programmer Bram Cohen for sharing large files in an efficient manner. Initially, these large files were open-source programs being developed by programmers from all over the world.
2. A protocol is a set of rules governing the communication of electronic devices.
3. A peer is a computer (e.g. your computer) which participates in file-sharing.
4. Bittorrent is different from other peer-to-peer software in that it divides a large file into many separate chunks which you can download non-sequentially from other computers or peers.
5. A tracker is a computer which coordinates the sharing of files among peers.
6. A torrent is a set of metadata or "data " about the file(s) you are downloading.
7. A seed is a computer which has a complete file.
8. Peers and seeds make up a swarm.
9. Once you start downloading the files in a torrent, the tracker will "find" a swarm in which you can participate.
10. The more peers and seeds there are in a swarm, the faster you can download a file. In other words, the more popular a torrent is, the faster it is to download (the files it refers to).
11. Once you download a chunk of a file, you will be immediately sharing it with others, or uploading it to other peers.
12. Download usually starts slowly, because the tracker is still looking for other seeds and peers which you can communicate with. Eventually, the download gets faster as more seeds and peers "congregate" in your particular swarm.
13. A Bittorrent client is a software program (aside from, and including the original Bittorrent program) which you can use to download torrents and the files -- the movies, software programs, etc. -- they refer to.
14. In my experience, the best Bittorrent client program out there is µtorrrent, which you can pronounce as you-torrent, micro-torrent, mew-torrent, or mi-torrent. The safest and/or most practical way to say it is the first one -- you-torrent or u-torrent -- since it is also how you type the domain name or URL.
15. After downloading µtorrent, you can search in µtorrent's search box for files you want to download. Alternatively, you can go to btjunkie.org -- in my opinion the most comprehensive torrent portal/aggregator -- to look for a file.
16. Be careful not to download copyrighted material.
17. To try downloading a torrent now, go download the torrent of 'Elephants Dream', an open-souce or free movie made with the open-source 3D animation software Blender.
18. You can keep abreast of Bittorrent or torrent developments at TorrentFreak.com.

That's it. Happy downloading!