A standard way of communicating across a network. A protocol is the “language” of the network. A method by which two dissimilar systems can communicate. TCP is a protocol which runs over a network.
Internet Protocol (IP):
The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. The internet protocol provides for transmitting blocks of data called datagrams from sources to destinations, where sources and destinations are hosts identified by fixed-length addresses.
The internet protocol also provides for fragmentation and reassembly of long datagrams, if necessary, for transmission through small-packet networks. IP is a network layer protocol in the internet protocol suite and is encapsulated in a data link layer protocol. Each computer on the Internet has at least one IP address that uniquely identifies it from all other computers on the Internet. It is also called as connectionless protocol because there is no continuing connection between the end points that are communicating. The most widely used version of IP today is Internet Protocol Version 4 (IPv4).
TCP/IP (Transmission Control Protocol/Internet Protocol):
A communications protocol developed under contract from the U.S. Department of Defense to internetwork dissimilar systems. Invented by Vinton Cerf and Bob Kahn, this de facto Unix standard is the protocol of the Internet and the global standard for communications.
TCP/IP is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP program just as every other computer that you may send messages to or get information from also has a copy of TCP/IP.