Have you ever played with Jenga blocks? You know how if you take out the wrong block, the whole tower falls down? Well, in math, sometimes things can be like that too.
One thing that mathematicians study are shapes called Fano varieties. These shapes are like Jenga towers, in that if you take out certain blocks (or points, really), the whole shape will fall apart.
Now, imagine another game where you have to balance different shapes on a seesaw. You can tell if the shapes are balanced if the seesaw stays level.
Mathematicians are interested in whether or not a Fano variety is balanced, or "stable." They call this “k-stability.” It's important to know if a Fano variety is k-stable because it helps us understand how it behaves and how we can study it.
Overall, k-stability is a way of making sure that the Fano variety won't fall apart if we take away certain important points or parts of it. Just like a tower of Jenga blocks, if a Fano variety is k-stable, it will be able to stay together even if something small is changed.