Each computer on the Internet must have an IP address. If you use a PPP dial-up connection the Internet, to use Internet tools, it does not matter if you are assigned a random IP address by the PPP server for the duration of your call.
If you want to start a WWW server you will want a permanent IP address. If you want to connect a network to the Internet, you must have as many IP addresses as you have computers on the network.
For an Internet server or servers to become reachable by a friendly name, such as microsoft.com, rather than an IP address of 12 numerals, you must use a domain name. Most Internet service providers can register a domain name for your Internet service and provide IP addresses. Both are required to be seen and used by others on the Internet.
If you must apply for your own domain name or IP addresses, you should have a good understanding of the Domain Name System (DNS) and TCP/IP networking.