BitTorrent is a computer protocol that is utilized to legally share information between different client computers. This typically includes videos, porn, h4x, pr0n, and Microsoft Office. It uses a "swarm" method of file distribution, whereby the porn is broken down into individual molecules and digitally transmitted to the destination, where it is reassembled. By breaking up files into smaller pieces, it allows clients who are have not yet completely downloaded a file to still share the pieces they have downloaded, resulting in extremely fast downloads for all parties. It is estimated that 94% of all internet traffic is Bittorrent related. There are a large number of programs available at no charge that use the bittorrent protocol, as well as online services that specialize in bittorrent files. Because of the nature of the protocol, it is virtually impossible to get a virus or download a bogus file while using the bittorrent protocol.
edit Original design
Bittorrent was originally created by the RIAA as a method to allow fans to share music files. The protocol was instituted to allow customers the ability to check out the entire album before making a purchase, with the hope of increasing sales for worthwhile artists. After several failed attempts at creating popular websites (Napster, Kazaa, etc.) The RIAA purchased the domain name ThePirateBay.org with the hope of increasing demand for the free files by having a domain name that implies there was something "illegal" about downloading music.
To further enhanse the "cool" factor of downloading something for free, the RIAA began a series of lawsuits where they pretend to sue grandmothers and young children for this "illegal download activity". While it was obvious that no company in their right mind would actually sue innocent people like this, most of the public bought into the marketing campaign and demand for free music from The Pirate Bay (and other similar websites) increased dramatically. The "victims" who were allegedly sued were actually paid actors and actresses, whose job it was to continue and promote the ruse that downloading music (or any file, for that matter) was inherently illegal.
When compared to most marketing strategies, it is easy to conclude that this method of getting people to try music was extremely successful, but it had one negative side effect. By allowing people to download commercial music at no cost, and allowing them to listen to the music before making a purchase, they had abandoned their old busines model of simply telling the customer "what was cool" and expecting them to line up like drones to buy the newest Johnny Bravo CD. Once they allowed people to actually listen and decide for themselves, most decided that the heavily commercialized and over produced music was in fact no better than much of the independent music available.
The Bitttorrent Protocol has caused many wars between roommates sharing an internet connection. Torrent programs assume you have infinite upload bandwidth and will max it out unless they are configured not to. In other words, if one user is browsing browsing the interwebz while the other has 12 torrents going, the torrents will consume all of the upload speed, preventing the other user to do anything except play minesweeper.
While torrents dont typically contain viruses, the client programs sometimes have security vulnerabilities that will allow your computer to be hacked by the RIAA. Once the RIAA has complete control of your computer, it will begin to exhibit strange and annoying behaviors like opening up 4 meatspin tabs in your browser, or telling you that you have an STD in your registry. These problems can be fixed by purchasing fake antivirus programs from one of the RIAA's many phony websites. Once you give these websites your debit card number, your entire bank account balances are transferred to the recording industry to fund artists like Britney Spears and Faith Hill.
Another problem that arises with torrents are people who leech off them without returning the favor by seeding them. For those without a technical background, this is like anal sex without giving the reach-around. Selfish Assholes.