What is the difference between seeding and leeching on utorrent?

Seeders and leechers are essentially the same, except for one difference. A leecher is someone who, when they have completed downloading it, they stop seeding the file, which annoys many people. The site can tell because it tracks how long you're on after you complete your download. Some sites don't allow leeching and will not allow you to download a torrent in the future if it persists too much.