What is the role of an attribute in html

Answer 1

to further describe the element it is attached to.

if you know <a>click</a> is a link then by adding attributes you can give it more meaning and function

as an example you can add the href attribute to give the link a destination

<a href="//www.google.com">click</a>

now the link will take you to google when clicked

or

<a class="green">click</a>

now the link is the color green as long as your css defined the name green to be the color green

Answer 2

an attribute defines more information about what you what to do with a special tag
example
width=" 100%" size=" 50" etc ....