What does a buffer do in a solution?

Hint: We need to know that a buffer is a solution that can resist pH change upon the addition of acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable. This is important for processes or reactions which require specific and stable pH ranges.

Complete answer:
Now let’s study what buffers do? Buffers work by neutralizing any added acid (\[{H^ + }\]ions) or base (\[O{H^ - }\]ions) to maintain the moderate pH, making them a weaker acid or base. Let's take an example of a buffer made up of the weak base ammonia, \[N{H_3}\] and its conjugate acid, \[N{H_4}^ + \].On adding a base to a buffer solution, the hydrogen ion concentration decreases by less than the amount expected for the quantity of base added. The acid and its conjugate base consume the hydroxide ions. When acid is added, the concentration of \[{H^ + }\] increases, so the position of equilibrium moves to the left: the added \[{H^ + }\] reacts with \[{A^ - }\] in the buffer to produce HA, and so the added \[{H^ + }\] is removed and the change in pH is minimized.
When alkali is added, the \[O{H^ - }\] ions react with the \[{H^ + }\] in the buffer, decreasing the concentration of \[{H^ + }\].The position of equilibrium moves to the right, dissociating HA to produce \[{H^ + }\]and thereby replacing it in the solution and minimizing the change in pH.

Note:
We have to know that a buffer is a solution containing a weak acid and its conjugate base. A conjugate base is the ion you have left when an acid has donated its \[{H^ + }\] ion, so we can represent a weak acid as HA and the conjugate base as\[{A^ - }\].