Couldn’t you just jump off the ISS with a parachute?
No. It’s in orbit.
Someone else mentioned KSP, you could read Its Only Rocket Science for a plain English explanation of how the physics of this stuff works. Its short and well written.
SHORT EXPLANATION
An object in motion stays in motion.
Gravity pulls smaller things in towards bigger things.
So when a small object is zipping near a big object, it will try to pull it in, but the two velocities (direction and speed combined = velocity) are going to fight each other.
If an object is moving at the right velocity the two kind of cancel out where it just enters a loop around the big object. This is an orbit. Imagine if the planet was to your left. You're moving forward, planet's sucking you in to the left. If the two are equal, the average of the two would be you moving diagonally. Now what happens if you make a bunch of, like, microscoping diagonal moves? Its a curve. So you do a loop around the big object.
Jumping from the ISS wouldn't work because the ISS isn't like some plane that's flying. Rockets in general, in space, don't work that way. The only reason objects slow down when you cut fuel on Earth is air resistance, water resistance, ground resistance. Friction. Stuff "pushing back" on them, and over time that pushing back slows them to nothing, like when you let off the gas and the car coasts to a stop. In space there is nothing to do that, so you just burn fuel to get up to a certain velocity and then you'll keep sailing that way forever unless you flip the rocket around and burn in the opposite direction (cancel one velocity out with the other). This applies to things on the ISS, too. If a person pushed themselves off of the ISS, they'd drift away forever, but they'd still be orbiting at the same speed. It doesn't work that way on the ground when you jump out of a plane because that air's hitting you and you don't have a jet engine behind you to keep punching through it.
Again, with air/water/ground to slow you down, you have to keep applying fuel and will coast to a stop if you don't. Moving costs fuel, slowing down is free. In space, it costs fuel to get on a velocity and get off of it, but the moving itself is free. Imagine a car where you only have to touch the gas to speed up, and it only burns fuel when you touch the gas/brakes.
The only difference between a space station and a rocket is that the rocket has to punch its way through the atmosphere. In principle you could slap an engine on a space station and move it around. They do have small rockets to station-keep (correct small errors that over time get them out of orbit). Rockets are shaped the way they are to be aerodynamic for punching through the Earth's atmosphere, minimize air resistance. In space it doesn't matter, you can build things in any shape you want.
You've seen astronauts in the manned maneuvering units (throne-like jetpack-like things), right? They're in orbit too.
You mentioned reentry and burning up. Things burn up due to air friction. You'd have to be going pretty fast to burn and pretty long for it to matter, but something in space isn't going to burn until it's entered the atmosphere (not in space anymore).
What made Newton remarkable was that he took the common sense idea that things fall down , combined it with these orbits everyone knew about, and realized it could all be explained by the same force. Before him Aristotle taught that objects want to "fall" (get sucked in to the center of the universe, meaning Earth) and the heavier ones sink or whatever (so earth gets on the bottom, water sits on it, air sits above it). Celestial bodies were assumed to move about the Earth in circular motions rather than falling. They were just DIFFERENT. There's some thing about them being embedded in spheres of clear glass-like stuff.
After Copernicus and Galileo prove (using the Phases of Venus) that the Sun has to be at the center, Newton realizes that there is no fundamental difference between celestial bodies physics and physics down here. Instead it's all based on gravity that big sucks in little, and he comes up with our understanding of an orbit that we know now.
