p2p

 "Users download and share at the same time; as soon as someone receives even a single piece of Fokkers, his computer immediately begins offering it to others. The more files you're willing to share, the faster any individual torrent downloads to your computer. This prevents people from leeching, a classic P2P problem in which too many people download files and refuse to upload, creating a drain on the system. "Give and ye shall receive" became Cohen's motto, which he printed on T-shirts and sold to supporters" - p2p definition in a nutshell (Wired) 

File sharing is when people on the internet are able to upload a file onto the internet, and someone across the world can download that same file. P2p file sharing is basically torrenting, as it skips the server part, and instead directly uploads and downloads onto yours or someone elses computer via a platform such as Limewire or BitTorrent. 

Some examples are Limewire (now shutdown) and BitTorrent (still strong). These p2p file sharing sites have been the cause of much trouble with various movie and music companies, as many believe they are responsible for these businesses losing money via people illegally creating copies and distributing their products. I once received a letter in the mail from my ISP for downloading a video game when I was younger, because I forgot to turn off my internet while doing the download (whoops). They said not to do it again or else they would fine me $20,000