Here's why:
* Prepositional phrases start with a preposition (like "with") and end with a noun or pronoun (like "shovel").
* Noun phrases are groups of words that function as a noun. They usually include a noun and can include modifiers.
Example:
* Sentence: "The gardener dug a hole with a shovel."
* Prepositional phrase: "with a shovel"
* Noun phrase: "the gardener," "a hole"
The prepositional phrase "with a shovel" acts as an adverbial phrase, modifying the verb "dug" by telling us how the gardener dug the hole.