IP address is a unique combination of four numbers separated by dots (periods, full stops). The unique combination is needed to identify an internet device in the public part of the internet. Please note that inside of local networks computers and printers are usually set up to use local IP addresses which are not unique for the public part of the internet. In order to provide connectivity between public and local networks special gateways are used, commonly known as proxy servers and network routers. There are also IP addresses which are used only for requesting your local computer only, these are in most cases 127.0.0.1 and 127.0.1.