Prepositional phrases are groups of words that begin with a preposition and end with a noun or pronoun (the object of the preposition).
Examples of prepositional phrases:
* in the house
* on the table
* with my friends
* to the store
Sentences without prepositional phrases:
* The cat sleeps.
* She laughed.
* They ran.
These sentences express a complete thought without using prepositions.
Therefore, while many sentences use prepositional phrases for added detail and context, they are not a requirement for a sentence to be grammatically correct.