Okay kiddo, so you know what a rocket is, right? It's like a big, powerful machine that flies up into space. Well, sometimes people need to send stuff up into space too, like machines or food or even robots! That stuff is called cargo.
But how do we get the cargo into space? That's where the rocket comes in. The cargo is placed inside the rocket and the rocket launches into the sky. As it goes up, it gets faster and faster until it reaches a really high speed.
Now imagine you're running really fast and you throw a ball. The ball will keep going forward because of the speed you gave it. The rocket is kind of like that too. When it reaches space, it keeps going forward because of the speed it built up.
Eventually, the cargo gets to where it needs to go, like the International Space Station or maybe to explore other planets. Cool, huh?