Here's why:
* Prepositional phrases are groups of words that begin with a preposition (words like "on", "in", "to", "from", "with", "for", etc.) and end with a noun or pronoun (the object of the preposition). They function as adjectives or adverbs, modifying other words in the sentence.
* Verbs are the action words of a sentence. They describe what the subject is doing or being.
Let's look at an example:
* The cat sat on the mat.
* "On the mat" is a prepositional phrase.
* "Sat" is the verb.
The prepositional phrase "on the mat" modifies the verb "sat", telling us where the cat sat.
Prepositional phrases can be quite complex, but they will always have a preposition and an object, and never contain a verb.