IPv4 - Wikipedia
https://en.wikipedia.org/wiki/IPv4
Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched...
What is IPv4?
https://nfware.com/blog-what-is-ipv4
Let's review IPv4 addresses in more detail. IPv4 is the fourth version of IP, it is the basis of the Internet, and establishes the rules for the computer networks functioning on the principle of packet exchange.