@Ticomaya,
TCP is how computers communicate on the Internet.
When you open any connection, say to a web server, the session is opened using a three-way handshake. One packet to the server to ask for the connection, one packet from the server to acknowledge the request, one more packet to the server to confirm that the connection is open.
127.0.0.1 is called the local loopback address. Every computer using TCP/IP thinks that it is 127.0.0.1.