Can someone explain me the below CSS structure in your own words please?

I am going through learning path and came across this CSS. Cansomeone please explain me how does this works step by step in your own words please? I know basics of CSS but I want to understand this structure and how will it work.
1 answers

The indentation is weird, but other than that it’s pretty straightforward: every h1 element, every .h1 class and every direct child of a .h1 class has the first set of style properties.

Then every h2 element, .h2 class and direct child of  a .h2 class has the second set of properties.