Why do I need a Seeder on a torrent?

First, it helps with the speed of download. The more seeders there are on a torrent, the faster the download of the torrent. This happens because you are not downloading the torrent from the actual torrenting site. Instead, you are downloading from another user that has the downloaded torrent file on their computer.

How can I be a good seeder?

You can be a good seeder by maintaining a fast internet connection, keeping the files in the directory that allows others to download them, and keeping your BitTorrent client open as much as possible. A peer is a BitTorrent user who has part but not all of the file they want and is participating in a swarm to complete the download.

Can a seeder upload a file faster than a leecher?

In reality, its possible that one seeder might be able to upload the file at a much faster rate than another. Or, that one leecher is able to download a file at a much faster rate than another. It just depends on the internet connection.