How do Torrents work?

(Video at the end! Do Watch it!)

Torrent(s), Or More precisely BitTorrent, is an Internet protocol for file distribution. It employs Peer-to-Peer file sharing for distribution of data. Today it is the most popular way of file sharing. As BitTorrent's wiki says: 

As of February 2013, BitTorrent was responsible for 3.35% of all worldwide bandwidth—more than half of the 6% of total bandwidth dedicated to file sharing. In 2019, BitTorrent was a dominant file sharing protocol and generated a substantial amount of Internet traffic, with 2.46% of downstream, and 27.58% of upstream traffic.

What is the Conventional way of file transfer?

Whenever a "Normal" File transfer happens over a network, TCP, UDP or FTP protocols are used. Though These protocols have great differences, but they have one elementary similarity — They all have one Client and one Server, known as Client-server model. This model of file transfer had been used since the dawn of networking. This, is "Centralised" file transfer model.

Peer-To-Peer File Transfer Model(P2P)

This model is relatively newer, and is usually far more efficient than the contemporary model. This model uses a distributed approach. Each computer having the file acts as server collectively provides the other clients with the file. Once these clients have the file they can choose to act as a server. This model removes the dependency of the clients on one particular server and hence is less vulnerable to not be available. Also it eliminates the cost requirement of maintaining a server. This is "Decentralised" File Transfer Model.
This is the way Torrents work (No, There's a whole lot more. Keep readi- No. Im not doin that). The computers who act Server-like become "Seeders" or "Seeds", and the one downloading becomes "peers" of the torrent.

How do you download one?

For downloading a Torrent file, We need two things:

1. A client
2. A .Torrent file/Magnet link (A topic for later posts, M-A-Y-B-E)

How do Seeders and Peers communicate?

If peers need to download files, Peers need to know which computer to ask from. This information is supplied to them by online webservers known as Trackers. These servers list (or "track". Is there any difference at all? Not One.) the active seeds of each Torrent. Many torrents are supplied with multiple trackers for redundancy. However, this dependency was eradicated by the introduction of DHTs(Distributed Hash Tables), But still many torrents include trackers, as they increase the speed of seed discovery.

CONCLUSION