Why does the earth revolves* around the sun?

There are two balancing forces acting on earth when it revolves around the sun.

[Source:mathworks.com]

Gravitational force of attraction.
Law of Universal Gravity states that every body in this universe attracts every other body with a force which is called force of gravity. The force

#F_G =G (M_1.M_2)/r^2#

Where #M_1 and M_2# are mass of two interacting bodies, #r# is the distance between the two and #G# a constant.

It has the value #6.67408 xx 10^-11 m^3 kg^-1 s^-2#
In our case, one is the sun and other earth.

Centrifugal force.
Centrifugal force is a 'fictitious' force that appears to act on all rotating objects and is directed away from the axis of rotation.
It is given by the expression

#F_(centri fugal)=mromega^2#

where #m# is the mass of rotating object, #r# the radius of circle of rotation and #omega# its angular velocity.

These two forces balance each other and keep the sun-earth system in equilibrium.

-.-.-.-.-.-.-.-.-.-.-.-.
*in the question 'revolves' is preferred word as earth 'rotates' around its axis.