In baseball, when a pitcher throws a ball the ball will eventually hit the ground. It drops at the same speed as everything else, but because it’s moving so fast it hits ground a long way off.
The space station is a speed-ball thrown by a powerful pitcher, but instead of going 95 mph it’s going 17,250 mph, and it’s high up in a near vacuum so there’s almost no wind resistance to slow it down. But it’s still falling. There’s nothing to hold it up there and gravity is pulling it down.
It would crash to the ground if the ground didn’t keep curving out from under it.
This is how an orbit works. As a satellite falls toward Earth, it misses the planet and keeps going around and around.
Sir Issac Newton describes this process in a thought experiment called “Newton’s Cannon,” in the illustration below. There is a nice article called “Why does the moon revolve around Earth?” that explains this process in more detail.