How Torrenting Works: A Book Photocopying Analogy

This article contains minimal technical terms to make understanding BitTorrent easier for non-technical users.

BitTorrent, also known as torrenting, is a protocol that allows fast downloading of large files. So how is it different from normal file downloads?

When you download a file from the Internet, a server has to upload the file at the same time. What if the file is huge and thousands of people are downloading at the same time? The server, which is just a more powerful version of your computer, has limited upload speed too. Therefore, a typical file downloading is not an ideal solution to serve large files to huge amount of users.

BitTorrent comes in handy in this situation. Each user that downloads the file has to upload his/her downloaded part to other users at the same time. It is a form of peer-to-peer file sharing. Now, anyone can share a large file on the Internet without having to rent or buy servers, and torrenting reduces server loads too.

For more detailed explanation, here’s an infographic created based on Ben Mordecai’s awesome answer on Quora.

Note: Anyone who downloads the torrent file is considered a leecher. Leechers also refer to users who negatively affect the swarm by limiting upload speed to be less than their download speed and leaving right after the file download is completed (as mentioned in the infographic).

Here’s a deeper explanation on how torrenting works. You can also check out Wikipedia’s more technical and boring version.

Thanks to CarlCheo.