IPv4 - Definition from the Hotspot Shield Glossary
Internet Protocol Version 4 is the most widely used protocol for data transferal and communication in networks. IPv4 provides device identification in the form of an IP address and creates a logical connection between different network devices.
IPv4 is used in packet-switched layer networks like Ethernet and is classed as a connectionless protocol. An IP address generated by the IPv4 protocol is a 32 bit address and is split into 4 blocks, for example 192.168.255.255. There are 5 different classes of 32 bit IP address from A to E each of which have a different subnet mask and use. Due to this 32 bit nature, IPv4 has a limited amount of IP addresses that can be created hence the creation of IPv6.