What is the difference between :before and ::before?

Question

I just saw a CSS code that included ::before tag. I looked at MDN to see what the ::before is but I really didn\'t understand it.

Can some

Answer 1

This distinguishes pseudo elements from pseudo classes.

The difference between pseudo classes and pseudo elements is described at http://www.d.umn.edu/~lcarlson/csswork/selectors/pseudo_dif.html