What is the difference between the selectors “.class.class” and “.class .class”?

Question

What is the different between .class.class and .class .class?

Answer 1

.class.class can also be used avoid the use of !important in case that a higher specificity selector prevents your rule from being applied.

In this case there are not two classes in an element. You just repeat the class which specificity you want to increase, like

(HTML) 
...

(CSS) .something.something {}