IP address it contain two parts.
Network Address is the first part of IP Address which is uniquely identify the network in the large TCP/IP network environment. Each Network contains there own network address on the internet and that the other network which it communicates. NIC-Network Information Center it is required unique network address for every organization. The unique network number is added to the packet which is sent from the network on the internet.
Host address is used Identify the system in the particular network. Therefore IP address is need every unique Host address in the network.