Explain how a Buffer acts to resist pH change in a system upon addition of an acid or a base

Explanation has been given below.

Explanation:

A buffer consists of either of a weak acid along with it's conjugate base or a weak base along with it's conjugate acid. Let's consider a buffer consists of a weak acid along with it's conjugate base If we add an acid to this buffer then conjugate base gets protonated and converted to corresponding weak acid. So effect of addition of acid gets neutralized by forming weak acid rather than increase in concentration of proton in solution. If we add a base to this buffer then weak acid gets converted to corresponding conjugate base. So effect of addition of base gets neutralized by forming conjugate base rather than in crease in concentration of hydroxyl ion in solution.