While Isaac Newton's law of universal gravitation is a very accurate description of gravity for most everyday situations, it breaks down when dealing with very strong gravitational fields or very fast speeds. Einstein's theory of general relativity provides a more complete and accurate description of gravity, which has been verified by numerous experiments and observations.

Here's a summary of the key aspects of general relativity:

* Gravity as curvature of spacetime: Instead of a force, general relativity describes gravity as a consequence of the curvature of spacetime caused by mass and energy. Think of a heavy object placed on a stretched sheet, causing a dip in the sheet. This dip is similar to the curvature of spacetime around a massive object.

* Motion in curved spacetime: Objects move along paths dictated by the curvature of spacetime. This explains why objects fall towards the Earth, not because of a force, but because they are following the curvature of spacetime caused by the Earth's mass.

* Gravitational lensing: The curvature of spacetime can bend light rays, causing them to be deflected around massive objects. This phenomenon is known as gravitational lensing and provides strong evidence for the validity of general relativity.

* Black holes and gravitational waves: General relativity predicts the existence of black holes, regions of spacetime where gravity is so strong that nothing, not even light, can escape. It also predicts the existence of gravitational waves, ripples in spacetime that travel at the speed of light. These predictions have been confirmed by observations.

While general relativity is currently the best theory of gravity we have, it's important to note that it's not perfect. There are some aspects of gravity that it cannot explain, like the behavior of dark matter and dark energy, and there are still some unanswered questions about the nature of gravity at the quantum level.