A rockets gets into space by burning enough fuel to provide the thrust needed to overcome Earth’s gravity. This is a lot. When you look at a rocket most of it is actually fuel with a tint space for the satellites on top. This means once it gets into space it usually doesn’t have enough fuel to stay in orbit and falls back to Earth. The rocket gives enough of a boost to the satellites to help them stay in space – sometimes they need to use some of their own fuel to get to the right orbit. The way they stay in orbit is by going just fast enough to escape Earth’s gravity, but not fast enough to escape.
I like Camilla’s answer.
My way of thinking about how satellites stay in orbit is to think of them as if they are falling around the Earth, but just missing. Sometimes they need a bit of help to stay up, so they have their own thrusters to give them a bit of a boost.