Breakdown of Na podwórku dzieci zostawiły rower obok ławki.
Questions & Answers about Na podwórku dzieci zostawiły rower obok ławki.
Because na podwórku is a prepositional phrase meaning in the yard / in the courtyard. In Polish, when you say where something happens, you usually need a preposition plus the right case ending.
Here, na means location, and podwórko changes to podwórku because it is in the locative case.
Because Polish and English do not always match prepositions directly. Even though na often means on, with some places Polish uses na where English uses in.
So na podwórku is the normal Polish way to say in the yard / in the courtyard. It is something you largely have to learn as a set expression.