When creating an IPv4 address there are a number of different types of addresses that can be specified. These include:

Which one chosen will depend on which method most easily yet accurately describes the addresses that you are trying to include with as few entries as possible based on the information that you have. For instance, if you are trying to discribe the addresses of a specific company’s web server but it you have no idea of how extensive there webserver farm is you would be more likely to use a Fully Qualified Domain Name (FQDN) rather than a specific IP address. On the other hand some computers don’t have FQDNs and a specific IP address must be used.

The following is a more comprehesive description of the differnt types of addresses.