Basic summary in my own words:
TCP: Sends a packet using a 3 way handshake. Good for authentication and such.
UDP:Sends a packet. That's it. It(the originator of the packet) is never informed if it got to it's destination. Good for when you need to stream a lot of data, like when you watch a video online.
Internet(aka TCP/IP) is just what it says. It delivers packets via TCP by using your IP.
That's a very overall simplistic definition.