Question

what is gravity?
what is called atmosphere?

Answer 1

a force which is present bw all things on the earth.
the blanket of air which surrounds the earth

Answer 2

Gravity :

It is the force that attracts a body towards the centre of the Earth, or towards any other physical body having mass.

Atmosphere :

The atmosphere is the blanket of gases which surrounds Earth. It is held near the surface of the planet by Earth's gravitational attraction.