What are seeds and leechers (peers) in torrents?

Number of seeds and leechers (peers) play an important role in determining the download speed of torrent file. So what exactly is meaning of torrents (bittorrent, utorrent) seeds and leechers?

What are seeds?
A seed is a client that has a complete copy of the data of a certain torrent. Once your BitTorrent client finishes downloading, it will remain open until you click the Finish button (or otherwise close it). This is known as being a seed or seeding.

What are leechers?
A leecher is a client that is currently downloading the data of a torrent. A leecher does not have the complete file, otherwise it would be called a seed.
Conclusion:
Seeds have the complete file and are actively sharing ... peers are downloading the file and have part of it and usually are sharing pieces also ... high numbers of each are best for speed ... low numbers of seeds and high peers will make it slow .. low numbers on each will make it slow ......