What is a Transmission Control Protocol with Internet Protocol?

A "protocol" is a set of rules used in networking, for a particular purpose.

IP (the internet Protocol) is the protocol used to transmit packets over various networks.TCP (the Transmission Control Protocol) is the protocol which (among other things) ensures a high degree of reliability over inherently unreliable networks. That is, individual IP packets may be lost, but TCP ensures that they are retransmitted.

TCP/IP is a protocol suite - in other Words, a group of related protocols. It is named after two important protocols, explained, above, but it actually includes various other protocols as well.