This work examines peer to peer networks and their usage on specific examples. Starting with the concept of peer to peer, it goes on trough history and ends with peer to peer today. You can see many ways of making peer to peer happen and how efficient those ways are. By comparing peer to peer with other systems all the advantages and flaws of peer to peer become clear. Flaws of peer to peer are obvious when it comes to the question of security as well. Moreover, peer to peer is the main tool pirates use for distribution of their illegal copies of products. However, the numerous applications and protocols that use peer to peer show it's popularity, therefore the most famous peer to peer protocol, BitTorrent, is closely examined in this short work. The way how BitTorrent works is explained with addition of some popular phrases that the users of BitTorent use. In the end, the representation of peer to peer on the Internet in recent past is explored, where it becomes clear how usefull peer to peer nowadays actually is.