Stands for Internet Protocol Version 4. A numerical address assigned to each device connected to a computer network. IPv4 defines an IP address as a 32-bit number divided into four 8 bit octets, and is usually expressed as a dotted decimal number each ranging from 1 to 254. Eg:
192.168.1.2
With IPv4 you can have a maximum of 4,294,967,296 devices.