What is the use of class="submit" in submit button?

Question

Plz explain

Answer 1

it's just a selector for CSS or Javascript ....
etc.
In CSS :
.submit {
color:red;
}

In Javascript :
document.getElementById("submit");

Answer 2

The class attribute was used to specify the name refer to the style in CSS.

That means it may refer to something like:-

.submit { color: rebeccapurple; }

in the CSS which change the text color of the submit button.

I've seen you already started the HTML course in SoloLearn and please take the CSS cource as well to learn more about it.