It is very difficult to think in more than three dimensions, so to visualise distortions in spacetime we need an analogy. Imagine spacetime as a two-dimensional rubber sheet, upon which spheres of metal are placed. Each metal sphere will produce a depression in the rubber sheet, the depth depending on the mass of the sphere. If two spheres are placed close enough the depressions will merge and the smaller sphere will roll toward the larger. However, Einstein's General Theory of Relativity is not the only theory to have a go at explaining gravity.
Some physicists think that gravity is due to very small particles called gravitons.
This idea is not without precedent. The electromagnetic and weak nuclear forces have been found to be different aspects of a single electroweak force. At the most fundamental level, the electroweak forces are transmitted between particles by messenger particles. Some of these particles, called weak bosons, have been detected by experiments - this work won Carlo Rubbia and Simon van der Meer the Nobel prize for physics in 1984. Just as weak bosons are messenger particles transmitting weak nuclear force, gravitons are thought to be messenger particles transmitting gravity.