An IP address is an « Internet Protocol » address. It is unique and is used to identify any device connecting to a network. This is therefore not limited to computers but expands to smartphones, routers, modems or smart devices such as printers.
This address can be permanent or temporary, in an IPv4 (most common) or IPv6 format. The IPv4 format is composed of a series of numbers separated with periods, like so: 18.104.22.168