TCP is a way of Secure communication in which the network makes sure that everything that has been sent has reached its destination without any loss in the packets. It uses the Flags to communicate with the receiver and ask for a confirmation on each packet it sends. It also uses the flags to establish the connection with the receiver so that it can know that receiver is able and willing to receive the data. Here is a detailed description of the most common TCP Flags and their function.
TCP stands for Transmission Control Protocol. Just like humans, Computers also require language to communicate with each other. TCP/IP is a common language which most of the modern computers share to communicate to each other.