A relative URL refers to a web address that points to a domain of a select website without including its full name. Relative URLs are useful because they make it easier to manage links within a website, especially if you need to move things around or change your website’s domain. They keep links consistent and simple.
Here is an example.
This is a full URL: http://www.example.com/images/pic.jpg,
The relative URL of this site is images/pic.jpg.