Learn Russian: Мужчина медленно катил её коляску вверх по улице. - The man was slowly pushing her stroller up the street.

Катить is the unidirectional verb of motion for rolling or conveying something on wheels. It is used here because the man is actively pushing the stroller in one specific, continuous direction—up the street. If he were pushing it back and forth to put a baby to sleep, or just walking it randomly around a park, you would use the multidirectional катать.

The English translation says "pushing", but doesn't катить mean "to roll"?

Yes! In Russian, you don't typically use the direct translation of "push" (толкать) for wheeled objects like a stroller (коляска), a shopping cart, or a bicycle. Толкать implies shoving something with physical force, whereas катить specifically means propelling an object smoothly on its wheels.

Why do we need both вверх and по to say "up the street"?

Вверх provides the direction ("upward"), while по + the dative case (улице) indicates the path/surface ("along the street"). Without вверх, по улице just means "along the street" (which could be perfectly flat). Together, they capture both the trajectory and the path: "up along the street."

Does коляска specifically mean a baby stroller?

It depends on the context. While it is the standard word for a baby stroller (детская коляска), it is also the standard word for a wheelchair (инвалидная коляска). Without further context, the man could be pushing either one.