TCP - This is a network protocol that ensures that if you send your data it will get there. Using this protocol is like having a phone conversation. You are connected directly to the remote site and data is send back a forth between the two. Because it is reliable, TCP is considered to be slower than UDP, most internet protocols (HTTP, FTP etc) user TCP



UDP - This is a conectionless network protocol. The best description I have found is UDP is like putting a letter in the post, it has an address and you send it, but you have no idea if it will get there. On LAN's UDP is quite reliable, over the internet it's not as reliable as TCP. However allot of games use UDP because it is faster and has a lower overhead than TCP.