what does "links can be used either absolute or relative" mean??

Answer 1

An absolute link is the entirety of a file path/directory. This causes problems if it's ever moved, and they can get very long. Ex: "C:/Users/User1/Desktop/..."
A relative link is like a shortcut for writing links. The link automatically starts where your page is, and you just add anything extra.
If a file is in the exact same folder, you could just write, for example, "Photo1.img".
If it's a few folders deeper in, include them in the link, like "/images/Photo1.img".

Answer 2

thanks