Fallturm Bremen is a really tall tower that is designed to help scientists test what happens when things fall or float in a special way called microgravity. Think of it like being in space where everything seems to float and you can't tell what is up or down.
When scientists want to do experiments in this kind of condition, they can't just go into space, because it is very expensive and dangerous. So they use a tower like Fallturm Bremen which is tall enough to give the sensation of weightlessness for a short time.
When the scientists put their experiments inside a capsule and drop it down the tower, it falls really fast but for a short time it also feels like everything it is floating which helps them to understand how different objects behave in microgravity situations.
This tower is really cool because it allows scientists to do complex experiments and research on gravity and space without having to travel all the way up to space.