This is the 14295th most frequent German word.
hinterm
"Hinterm" is a colloquial contraction in German meaning "behind the."
In this sentence, 'hinterm' is a contraction of 'hinter dem', which is a preposition combined with a definite article, used with a locative meaning, indicating the dog is located behind the sofa.
Der Hund schläft hinterm Sofa.
The dog sleeps behind the sofa.
Here, 'hinterm' functions similarly as in the previous sentence, indicating location, specifically stating that the child is hiding at a location behind the tree.
Das Kind versteckt sich hinterm Baum.
The child hides behind the tree.
'Hinterm' in this context again forms part of a prepositional phrase indicating the location, specifying where the car is being parked in relation to the building.