what does class do here?

Question

<input type="submit" value="SEND" class="submit" />

Answer 1

The class is like a tag or name, you can find this node with the class, for example in JS:

var x = document.getElementsByClassName("submit");

Answer 2

It allows you to grab elements by group name (i.e class name). Like 'id' attribute which allows you to grab individual element. Hope it helps :)