Host address

In network addressing, the host address, or the host ID portion of an IP address, is the portion of the address used to identify hosts (any device requiring a Network Interface Card, such as a PC or networked printer) on the network. The network ID, by contrast, is the portion of the address that refers to the network itself.

Example:

Your local network has an address of 192.168.1.0 /30 (using CIDR notation for this subnet or in other words with subnet mask 255.255.255.252).

Your network ID is the first 30 bits, in bold below. The host ID portion is the last two bits. By changing those two bits, you can create the following IP addresses:

...
Wikipedia