Ip datagram

Tcp/ip is a combination of tcp(transfer control protocol) which is present in transport layer of tcp model and ip(internet protocol) which is present in network layer. TCP provides reliable connection and ip provides unreliable connection.
Tcp adds TCP header at the beginning of application data which is known as TCP segment. And ip adds ip header at the beginning of this tcp segment which is known as ip datagram.
UDP provides unreliable connection. Udp adds udp header at the begining of application data and is known as udp datagram. And ip adds ip header at the beginning of this udp datagram which is known as ip datagram. Udp stands for user datagram protocol.