A seeder is a peer that has a complete copy of the torrent and still offers it for upload. The more seeders there are, the better the chances of getting a higher download speed. Among users of the BitTorrent file distribution protocol, a leech is a user who disconnects as soon as he/she has a complete copy of a particular file.
However, most sites prefer the term leecher for all users who are not seeders (don't have the complete file yet). However, because BitTorrent clients usually begin to upload files almost as soon as they have started to download them, such users are usually not freeloaders. Therefore this kind of leeching is considered to be a legitimate practice.
Reaching an upload/download ratio of 1:1 (meaning that the user has uploaded as much as he/she has downloaded) in a BitTorrent client is considered a minimum in the etiquette of that network. A leech becomes a seeder (a provider of the file) when he or she finished downloading and continues to run the client. They ... more.