Answer 1

Absolute URL
Absolute URL need the entire address on the page that you link to.
<a href = http://www.sololearn.com>

Relative URL
The relative URL requied not the full address.
The page or image is on the same server.
you are dealing with local resources it is better to use relative URLs based on the document root.

<a href = "/xyz.html">
<img src = "/images/logo.png" >

for more information read this
https://stackoverflow.com/questions/2005079/absolute-vs-relative-urls