After Einstein’s Theory of General Relativity one would think we fully understand gravity. Sadly, that is not the case. In fact we understand gravity no more than Newton did. If anything, we understand it less.
Newton developed a simple equation and there was hope it would reveal the mechanism behind the force. Then Einstein showed the effects of gravity to be better modelled by the result of the interaction of matter with time and space. While General Relativity allows us to calculate the effects of gravity with more precision than we can measure, it gives us no more insight about the mechanism of gravity than Newton’s theory did. Fundamentally, we don’t understand gravity. If we did we’d know how to make gravity and anti-gravity, but we don’t and so far we can’t.
So, having a theory that correctly models and predicts reality doesn’t mean we understand it. In fact, we understand nearly nothing about gravity and nuclear forces which means we understand nearly nothing about matter. We just know how to model it really well. Keep this in mind when reading headlines about breakthroughs in understanding of something. It usually just means we have better, more accurate, equations.