TCP is a connection oriented protocol, provides error checks, guaranteed delivery of packets and also re-transmits the packets when dropped, flow control not to overwhelm the receiver. FTP, HTTP, HTTPS, SFTP, SSH (where guaranteed delivery is the motive) UDP is a connection less protocol, doesn't care if the packets are received by the receiver, no order maintained, no flow control, but makes the best effort to deliver the packets. UDP is faster than TCP. Video streaming, online games, DNS, DHCP Applications.