Theory of Relativity explained :
-Our universe has 4 dimensions (3space+1time) which together form a continuum known as the space time fabric.
-Gravity is not a force but the curvature of space-time around an object(general Relativity) .

Since, the space time bends around heavy objects, time slows down as you move closer to the center of heavy objects.
-Since light follows the curvature of space-time, it bends around heavy objects.

-The speed of light remains constant for observers in all frames of reference (special Relativity)
-As a result, time slows down and length contracts in the direction of motion of high speeds.

Also energy and mass are equivalent and can b related as E² =m²c⁴+p²c²or E=mc².
-The speed of light is the maximum speed that one can attain in our universe.