A CSS class , an attribute used to define a group of HTML elements in order to apply unique styling and formatting to those elements with CSS.
Example :
<!DOCTYPE html>
<html lang="en">
<head>
<title>Multiple Classes</title>
<style>
p.center {
text-align: center;
color: blue;
}
p.large {
font-size: 200%;
}
</style>
</head>
<body>
<h1>This heading will not be affected by style sheet.</h1>
<p>This paragraph will be blue and center aligned.</p>
<p>This paragraph will be blue, cetner-aligned, and in a large font-size.</p>
</body>
</html>
Show Output: