Every device that's connected to the Internet has a unique identifier known as IP (Internet Protocol) address. This includes computer systems, web servers, smartphones, switches, etc. The pool of addresses, which was introduced initially, is already distributed, so the so-called IPv4 IP addresses are progressively being replaced with IPv6 addresses. Every domain which opens an internet site has an IP record, that is the address of the server where it's hosted. With the IPv4 system, the record is called A and it is comprised of four sets of numbers from 1 to 255 divided using a dot, while in the IPv6 system it is called AAAA and it comprises of eight sets of hexadecimal numbers i.e. this sort of records use numbers from 0 to 9 and letters from A to F. An example of an AAAA record is 2010:0c48:43d3:2142:1012:8c3a:2475:2435 and this format works with a considerably larger number of IPs than the IPv4 format.