Every device that's connected to the web has a unique identifier called IP (Internet Protocol) address. This includes PCs, web servers, smart phones, switches, and so on. The pool of addresses, which was introduced at first, has already been distributed, hence the so-called IPv4 IP addresses are slowly getting replaced with IPv6 addresses. Every domain that opens an internet site comes with 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 made up of 4 groups of numbers from 1 to 255 split up by a dot, while with the IPv6 system it's called AAAA and it consists of eight sets of hexadecimal numbers i.e. this type of records use numbers from 0 to 9 and letters from A to F. An illustration of an AAAA record is 2010:0c48:43d3:2142:1012:8c3a:2475:2435 and this format supports a considerably bigger number of IPs in comparison with the IPv4 format.