What's the full maning of 'href' to html ?

Answer 1

href means hyperlink reference, it is used to specify the url of destination link of the resource

Answer 2

href represents an attribute that acts as the source anchor of a hyperlink independent of whether it has been visited👍

In other words:
A href is a attribute for hyperlinks or anchor links.

Additional:
https://www.w3schools.com/tags/att_a_href.asp