BitTorrent uses its own set of keywords to describe various aspects of how the system works. If you want to really understand what’s going on, it’s helpful to understand what the terms mean.
Seed: This is the machine that originally distributed the shared file. Technically, any peer that has 100% of the shared file also becomes a seed.
Pair: This is a machine that downloads the shared file and then shares parts of the file with other peers. When you run a BitTorrent client on your machine to get a file, you are running a peer.
Piece: Part of a shared file, which will be combined with other pieces when reassembled into a usable whole.
Torrent: Torrent is used in two ways. When specified with the word file (as in “torrent file”), it is a file containing metadata describing all the parts of the shared file and their checksum (validation) data. When used on its own (as in “I downloaded a torrent from Ubuntu”), it refers to the shared file (and all its parts).
Swarm: This is the entire network that shares a file, consisting of all peers and seeds.
Tracker: This is a server that keeps track of the swarm’s seeds and peers. A tracker is usually not involved in the actual transfer of data, but acts more as an index or search engine for people looking for torrents. Trackers are often the target of legal action, because they are seen as facilitators of illicit file sharing.
Leech: This is a term for a peer who does not share parts of a shared file. Basically, it is someone who wants to download a file using BitTorrent, but is not willing to do their part to support the swarm. Some leeches with very low bandwidth connections cannot download and share, so they download first and then share. But most leeches simply choose to be a “piggy” and download files without giving anything in return.
Health: Don’t confuse the BitTorrent term “health” with the quality or safety of a file. In BitTorrent, health means how much of a file is available for download (anything less than 100% means you won’t get a full file today). Don’t assume that something that shows 100% health is, for example, virus-free. This also highlights one of the downsides of torrents: not all files are fully available for download. You may have to wait until a couple show up with missing parts, or, in the case of less popular files, you may never get those missing parts.
Fake: A file that fakes what it claims to contain. Typically, this is a file that contains malware or just junk bytes, designed to attack users or boost file upload rates.
Relationship: This is a measure of how much you’ve uploaded. It is sometimes used by crawlers to allow greater access to more files.
HILL: People often get confused about this. HILL It represents The Onion Router and is not related to BitTorrent. Because TOR is a way to communicate anonymously over the Internet, some people run torrents through TOR. But the TOR Project and BitTorrent are completely separate entities.
Have I forgotten any important torrent terms? If so, let us know in the comments below.