What is the difference between TCP and UDP if they both operate at the Transport layer?

Although both TCP and UDP are Transport layer protocols and provide the same basic function, TCP is a connection-oriented protocol, which means a session is established before data is transmitted, and acknowledgments are sent back to the sending computer to verify that the data did arrive and was accurate and complete. UDP is connectionless; no session, or one-to-one connection, is established prior to data transmission. This makes UDP the faster of the two, and TCP the more reliable.