What is this class in css?

Answer 1

class has many use in style one of the main one is you will not have write styles again and again just make a class and put all elements with same role as of that class and
the styles will be applied

Answer 2

it is a selector,which generally select a group of elements(tags)
for eg.
<div class="one">
<P> Play</P>
<P> the</P>
<P> game</P>
</div>
now if in CSS
<style>
.one
{
font-weight:bold;
}
</style>
Then all the elements(P tags) in div will have Bold texts.
I hope I am clear.

Answer 3

parent element! you dont have to repeat things again and again to , just it will inherit by default