Adjectival phrases tell us more about the subject or the object in a sentence. Examples:
The school raised money for the local night shelter. The object is “money” and the adjectival phrase “for the night shelter” tells us more about the object.
The movie was interesting but terrifying. The subject is “movie” and the adjectival phrase “interesting but terrifying” tells us more about the subject.
Since the subject or the object can be a noun phrase, an adjectival phrase can tell us more about the noun phrase in a sentence. Example: The unemployed man on the street corner needs to find work. “The unemployed man” is a noun phrase (the subject of the sentence) and “on the street corner” tells us more about him.