IPv4 is the fourth version of the Internet Protocol (IP). It is a widely used network protocol for communication over the internet. IPv4 uses 32-bit IP addresses, allowing for a total address space of approximately 4.3 billion unique addresses.

An IPv4 address is typically represented as a series of four numbers separated by periods, such as 192.168.0.1. Each number can range from 0 to 255, providing 256 possibilities per number.

However, due to the exponential growth of internet-connected devices, the IPv4 address space has been nearly exhausted worldwide. This has led to the adoption of IPv6 (IPv6 is the latest version of the Internet Protocol), which uses 128-bit addresses and offers a much larger address space to meet the current and future needs of internet connectivity.