What is class attribute function?

Question

we see "class" attribute in so many html tags
what is it for?
what does it define?
and what are its values?

Answer 1

You Refer to an Element via class in Css and Js
its Same As Id
class by . and Id by #

<div class="E1">Text</div>

Css:
.E1{
background-color:red;
}

Js:
document.getElementbyClass("E1");