In CSS, you use a period (.) to indicate "match on class name" and the octothorp (#) to indicate "match on id".
color : magenta;
background-color : lime;
color : black;
backgroundColor : white;
<div class="funky" id="woof">This text will show purple on green</div>
<div class="funky" id="butNotMe">This text will be black on white</div>
<div class="funky" id="zing">Back to purple on green</div>
I think it would be worth your while to go back and catch up on HTML and CSS.
(Though jQuery uses "." and "#" in the same way as "selectors".)