A space fountain is like a really tall and cool water fountain in space! Imagine a big spout of water that shoots way up into the air, but instead of water, it's made of small metal pellets or balls.
At the bottom of the fountain, there is a machine that shoots the pellets up the fountain using something called electromagnetic force, which is like a really strong magnet.
As the pellets go up, they reach a specific point where they are moving at the same speed as the machine that launched them. At this point, they will stay in place and appear to hover in mid-air like magic!
The fountain uses this hovering effect to create a "chain" of pellets that stretches all the way to the top of the fountain. These chains are created by the magnet at the bottom pulling the pellets up, and then gravity pulling them back down.
The space fountain is not just for show, it can actually be used to help spacecraft move around in space without using up a lot of fuel! Cool, right?