So that Internet users do not have to remember the complex Internet Protocol addresses, domains are assigned to them. This is done through DNS, the domain name system. This way, users just need to remember the domain name and type it into the browser. This now queries the IP address assigned to the domain from a name server and is forwarded to the appropriate server. It is also possible to assign IP addresses manually in a private network.
A distinction is made between IPv4 and IPv6 addresses. The original version, IPv4, consists of 32 bits, which means that a total of 4,294,967,296 addresses can be represented – not enough to cover the rapidly expanding Internet. For this reason, the 128-bit IPv6 was introduced. Internet Protocol addresses are assigned by the IANA. This distributes IP addresses in blocks to various regional sub-organizations, which in turn forward the addresses to Internet providers. In this way, the addresses reach the customers of Internet service providers such as centron. Here customers can rent domains servers and register domains that are assigned to a unique IP address.
You can find more information about IP here.