BitTorrent is a peer-to-peer (P2P) file distribution tool written by programmer Bram Cohen which debuted at CodeCon 2002.
.torrent files are one of the more popular methods of sharing files across the internet, and can be used by any torrent compatible file sharing application. .torrent files are very small as they do not contain the actual data you wish to download, instead they contain general text information such as the name of the file you wish to download, its size, the internet location where the data tracker (see below for more info) can be found, and a checksum used to ensure you are downloading the correct file.
As .torrent files are so small, they are easily shared and there are many hundreds, if not thousands of websites sharing .torrent files in their P2P networks. Once you have the .torrent file, you will need a torrent compatible P2P file sharing application. One of the most popular is the original BitTorrent (link below). Once installed, you can either double click the .torrent file through Windows explorer or open the .torrent file directly through BitTorrent.
Once opened, your chosen application will attempt to talk to the data tracker for that file. If the tracker is online, the data tracker will reply telling your file sharing application where every available source of the file can be found. These sources (also known as seeds) are other users that already have the file that you are looking for and wish to share the file with you. Your file sharing application will then begin to download from these seeds until you have the complete file.