Question

When a bullet is fired from a gun the gun gives a kick in the backward direction explain

Answer 1

Hi friend here is your answer.

###############

Its according to newton's 3rd law every action has a reaction.

###############

Answer 2

There is something known as conservation of momentum.

Momentum is is the quantity of motion possessed by a body.

According to law of conservation of momentum the total momentum before collision is equal to the total momentum after collision.

Hence to conserve momentum the gun moves backward when the bullet moves forward.
It also takes place due to the Newton's third law of motion with states that everybody has an equal but opposite reaction.