Prepositions are usually followed by a noun or a noun phrase.

Kate's birthday is in the middle of January.

Josie was hiding behind the curtains.

They travelled by car.

The preposition and the noun phrase together are called the prepositional phrase.

preposition + noun phrase = prepositional phrase

There was a playground next to the school.

The dragon flew over the hills, breathing fire dejectedly.

Sometimes the word order of a sentence can be changed so that the sentence starts with the prepositional phrase.

Next to the school there was a playground.

Over the hills flew the dragon, breathing fire dejectedly.

Changing word order in this way can make writing more varied and interesting, but it doesn't work for all prepositional phrases.

Jane played with Chloe.

With Chloe Jane played.      This doesn't work!