Surely you've heard of the Theory of Relativity? There are entire libraries full of books on the subject.
I'm smart, but no Einstein. What does what you said mean?
It means that, in the real world, the shortest distance between two points isn't quite a straight line. In fact, it can be far from straight. Do you see the long, curvy things in this picture? Those are distant galaxies. Their images are distorted because the light from them always travels along what is locally the straightest path available; globally that means it curves around heavy objects (in this case, an intervening cluster of galaxies).
So we know that gravity bends light. So what? It is just proof that gravity exisists, and that light probably has some sort of mass. What is gravity?
PS, without my work, you may have not had that super Hubble picture you posted.
