How do buffers maintain pH?

Hint: In organic chemistry, we have studied about acids, bases and buffers. We know that a buffer is defined as an aqueous solution that consists of a mixture of a weak acid and its conjugate base or mixture of a weak base and its conjugate acid.

Complete step by step answer:
We must remember that in many reactions and solutions, buffers are used as a means of keeping pH at a nearly constant value in a variety of chemical reactions. The pH change is very less when a small amount of strong acid or base is added to the buffer solution.
Buffers resist pH change on the addition of an acidic or basic component. It has the ability to neutralize small amounts of added acid or base while maintaining the pH of the solution for stable reaction.
As we know that every buffer has certain buffer capacity and buffer range be it an acid buffer or a basic buffer. Buffer capacity is defined as the amount of acid or base that can be added before the pH changes.
Let us assume, we are adding a weak acid with its conjugate base to form a buffer solution. In aqueous solution, the weak acid does not dissociate completely. Only a small amount of hydrogen cation is dissociated with the conjugate base anion.
If we add hydrogen cations (acid) to the solution, it will react with conjugate base and reform acid, which will keep the pH nearly constant.
If we do vice-a-versa, again the solution will have a nearly constant pH value.
Thus, buffers are essential to maintain a constant pH in reactions.

Note:
We need to remember that the buffers are well used for reactions that require a constant pH value during a reaction. Buffer solutions are known to have an active pH range and capacity that dictates how much acid/base can be neutralized before pH change and also it determines the amount by which it will change. In blood, a bicarbonate buffering system is used to regulate the pH of blood. In industry, buffering agents are used in the fermentation process and in setting correct conditions for dyes used in colouring fabrics.