Absolute URL

An absolute URL is one which has a full URL specification, meaning it has a fully qualified domain name. An absolute URL includes the service, the host name, and the full path name of the file. For example:

http://www.nasa.gov/hqpao/library.html

This absolute URL has specified the http service on the system www which resides in the nasa.gov domain, and is asking for file library.html which is in the /hqpao directory.

It is better to use a relative URL instead of an absolute URL for two reasons.

It is easier to move a group of related HTML documents to a different directory or a different server, without modification, if you use relative URL specifications.
The system does not have to go out and find the same IP address again, thus finding the requested document more efficiently.

Since a relative URL is better, tell me more about it.