prepositional adjective phrase

A prepositional phrase is a phrase that begins with a preposition. There are over 150 prepositions in English -- some of the most common are: of, to, in, with, for, by.  

In my two sentences above, I used several prepositional phrases -- "with a preposition", "in English", and "of the most common".

Prepositional phrases can serve as either adverbs, which modify verbs, or adjectives that modify nouns. "Learners of English" contains a noun "learners" and a prepositional adjective phrase "of English" that modifies the noun. The prepositional adjective phrase always follows the noun it modifies.

Compare that to simple adjectives that fall before the noun. In many cases, a prepositional adjective phrase can be rearranged as a simple adjective.  "Drivers of cars" can be said simply as "car drivers".