You know how sometimes your toys don't look like they're standing up straight, but they're kind of wobbly or tilted? That's kind of like what happens to molecules too. Sometimes the atoms in a molecule look like they should be straight and stable, but they start wobbling and tilting instead.
Scientists call this wobbling the Jahn-Teller Effect. It happens because the electrons in the molecule are arranged in a way that wants to make the whole molecule symmetrical. But if the molecule is symmetrical, then one of the atoms might be in a spot where it's not quite happy.
So, to make the whole molecule more stable, that atom starts wobbling and tilting out of place. It's like if you and your friend were sitting on a seesaw, but you were both the same weight. You wouldn't be able to balance, so one of you would need to move a little bit to make it work. The same thing happens with these molecules - one atom needs to move to make everything more stable.
Scientists study the Jahn-Teller Effect to understand how molecules work and how they can be used in things like medicine, electronics, and more. It's a complicated concept, but it's really just about atoms wobbling around to make everything work better.