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

Code Example 1

To specify multiple classes, separate the class names with a space,
e.g. <span class="classA classB">.
This allows you to combine several CSS classes for one HTML element.

Code Example 2

//HTML Code
<div class = 'firstClass secondClass'></div>

//CSS Code
.firstClass.secondClass {
  
}

Code Example 3

<div class="a-class another-class"></div>

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