Torrents are the application of P2P technology.
“A peer-to-peer (or “P2P“, or, rarely, “PtP”) computer network uses diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of servers provide the core value to a service or application. ” stands the definition of P2P according to wikipedia.
Let me explain this, we download say a software(ok its FREE software say Linux distributions), if 10 people are downloading from a central server which has a bandwidth or Line speed of 1Mbps upload. Then the maximum speed the ten people will get is 100kbps(for keeping it simple we will consider 1000kb=1Mb). Even if say all of these individuals are having a 512 kbps line, the maximum speed they will get is a shared value of server.
But now say i download a part of the file from server and share it again so everybody else can also download from me then the speed increases, think all these 10 people are downloading and as well uploading with 512 kbps. Then the total downloading bandwidth is 1000+ 10*(512) = 6000 (approx). That is the average availabilty has increased by 600% and each user will download at full speed of 512kbps. Now the speed of download is not limited by servers speed but by the users own line speed.
And in a pure P2P network there is no server, everybody is equal.. everybody is your equal soul a peer, and hence P2P.
Terminologies in P2P :
Tracker : The system or application or Server which mediates the communication between the peers.Tracker is needed for peers to initiate the communication with other peers, but once communication is established tracker is not needed. Trackers are hosted typically in a website like Piratebay or other torrent sites.
Seeder : The person who initiates the upload/shares the file.When a leecher completes his down and shares it he also becomes a seeder.But many leechers do not share once their download is complete this is called as leeching.
Private Tracker : This is a tracker which verifies the amount of data downloaded and uploaded by a leecher and maintains rules. Basically a private tracker increases availability on a torrent network by making more leecers to share.
What do I need to get into P2P and use torrents ?
How can I start downloading?
Go to your favorite torrent site and download the bittorrent file ie *.torrent. Open it , it will by default open in your torrent client. It will ask for a port number choose any number between 40000-60000. This is the port you have to setup Port forwarding in your modem/router.(we will look at this again)
Is it legal?
If downloading a movie/music online it mostly is illegal. But then its your choice.But there are lots of legal content on torrent sites.