Transmission control protocol accepts data from a data stream, divides it into chunks, and adds a TCP header creating a TCP segment. The TCP header is the first 24 bytes of a TCP segment that contains the parameters and state of an end-to-end TCP socket. It is used to track the state of communication between two TCP endpoints.

For a connection to be established or initialized, the two hosts must synchronize. The synchronization requires each side to send its own initial sequence number and to receive a confirmation of exchange in an acknowledgment (ACK) from the other side

The below diagram shows the TCP Header format: