A prepositional phrase is headed by a preposition and completed by a noun or noun phrase:
in bloom in great haste on the piano under the radar with a smile
They can be attached to a noun:
See the jacarandas
in bloom!
It’s service with a smile.
or attached to other prepositional phrases:
They received letters from the family on the coast of New South Wales.
Prepositional phrases often serve as adverbial phrases or adjuncts to modify the verb:
He left the room in great haste. [in great haste modifies left]
They put the flowers on the piano. [on the piano modifies put]
Prepositional phrases are very common in descriptive and expository writing.
