Einstein’s happiest thought of in his life, was that realization of gravity is not a force at all, but is indistinguishable from, and in fact the same thing as, acceleration. This idea he later called the “principle of equivalence”.
According to this idea, objects behave in a gravitational field in a similar way as accelerating objects. For example, I would feel the same attraction or the force to the flow of this house (as I’m on this Earth) if this house were to accelerate upward at a rate of 9.807 m/s² in empty space.
With this idea Einstein realized, gravity is not really a force at all, but just the result of our surroundings accelerating relative to us. Also he concluded Space and Time will create this gravitational illusion when it wrap the space-time fabric around the massive objects.