Check out example codes for ". and # in css". It will help you in understanding the concepts better.

Code Example 1

<!DOCTYPE html>
.classname {
  background-color: green;
  color: white;
#idname {
  background-color: pink;
  color: white;
<div class="classname">I am  green colour<div>
<div id="idname">I am  pink colour</div>

Code Example 2

.myclass {
  border:1px solid black;
  background-color: #d2d2d2;
/*If you give this class to a div in html, it will get the styles you gave
to that class. You can add multiple classes to a div, and multiple divs
can get that class. */
/* I hope I helped! */

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