Think of IP as something like the postal system. It allows you to address a package and drop it into the system, but there is no actual direct "link" between you and the recipient. Instead, there is a "web" of links interconnecting with each other. This is where IP and TCP come in. IP tells packets what their destination is and how to get there; TCP ensures a reliable connection, checking packets for errors, requesting a "re-transmission" if it detects one.