Is there a site/link or a section in a typical grammar book that explains that? - How the objects of somethings gets treated as a noun as a whole? I guess what I am asking is: What do you call that terminology wise?
The clauses in red are more obviously clauses acting as noun objects of the preposition. I don't think there is any further term. Clauses can function as most any part of a sentence except the verb.
What you're eating looks repulsive.
I cannot see over the fence without standing on a box.
Sitting on the fence, the bird could see both gardens.