Imagine you have a big, bouncy ball. If you looked at the ball from far away, it might look like a perfect circle. But if you got close and looked very carefully, you would see that the ball actually has little bumps and dips all over it. These bumps and dips change the shape of the ball in different ways.
Now, imagine there was a special machine that could measure exactly how curved the ball is at each and every point on its surface. This machine would give you a set of numbers that describe the shape of the ball in a way that doesn't change, no matter how you twist or stretch or squish the ball.
These numbers are called curvature invariants. They are like a special code that tells you everything you need to know about the shape of the ball, without you having to actually see or touch it. Scientists and mathematicians use curvature invariants to study all sorts of things, from the shapes of planets and stars to the behavior of particles in quantum mechanics.
So basically, curvature invariants are a way of describing the shape of an object that stays the same no matter how you manipulate the object. It's like a special language that helps scientists and mathematicians understand the world around us.