Explain the theory of relativity in a small sentence

Theory of relativity.

In the year 1905 a famous mathematician and physicist named Albert Eisenstein gave a theory which shows relation between time and motion.

yes i am talking about special theory of relativity.

actually theory of relativity is divided in two parts

1. special theory of relativity

and

2. general theory of relativity.

✔special theory of relativity is based on the time and motion. 

there are two frame of references.

1. inertial frame of reference

and

2. inertial frame of reference.

in inertial frame of reference we talk about when body is moving with constant velocity.

and

in non inertial frame of reference we talk about unconstant velocity.

in the special theory it is used that the time and motion are relative. 

and there is a postulate that

✳ Nothing can travel faster than the speed of light that is.

299692458m/s and universe is limited at this speed so if a object moves near the speed of light then the time slows down for that object in order to maintain that speed.

Now

Theory of general relativity.

✔ after giving special relativity Einstein was not satisfied and wanted to know about how gravitational force can affect time.

so he gave general theory of relativity.

in this we talk about the gravitational force.

space time curvature 

fabric of cosmos and many more thing

in this Einstein showed that how gravitational force affect the time and also showed that the planets revolve around the sun because of the curve in space time