Absolute Link: An absolute link is a hyperlink that contains a full URL. This URL includes all information needed to locate a page, document, site, or other item on the internet that can have a web address.
This information includes the protocol, which can be found in the form of Hypertext Transfer Protocol or File Transfer Protocol (HTTP and FTP), the domain name of the source website, the location in the directory or sub directory where the item is located, and the name of the file type, if necessary.
Absolute links are always singular and unique, and they're ideal for links posted to pages which are outside the main domain or directory.
These links differ from relative links, which can consist of just a file name, since links don't have to be unique withing their own directory or domain. When a browser registers a relative link, it understands to find the site in the same directory or domain where it found the relative link. Relative links often load faster because they don't have to go through the entire web.
Essentially, absolute links provide all the information for a browser to locate a file or page in one place, as opposed to relative links, which are extrapolated by the browser and are used for navigation within a domain.
An absolute link would look something like this:
https://www.yoursite.com/photos/image.png
While a relative link would look something like this:
/photos/image.png