Internet Protocol (IP) is the foundation under TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). IP belongs to the Internet Layer in the OSI model.
Although IP by itself is not very useful, it establishes the standards to allow a computer on the Internet to find/address another computer. This is why we refer to the network address of an interface as an IP address, and not a TCP address of a UDP address.
If you want to know how IP is used to route traffic across the Internet, you should take a formal class in TCP/IP. The focus of this module is on the comparison amongst the protocols.
To use a telephone analogy, IP specifies the standard for phone numbers, (3-digit area code plus 7-digit number), what area codes are valid, what are emergency numbers and etc.