How do buffers work?

Buffers work by neutralizing any added acid (H+ ions) or base (OH- ions) to maintain pH, making them a weaker acid or base. One may use a buffer made up of the weak base ammonia and its conjugate acid NH4+ as an example. When HCL is added to this buffer, the extra H+ ions added are consumed by the NH3 to form NH4+. Because all the H+ ions have formed a weaker acid, NH4+, the pH of the system does not change significantly. Similarly, when NaOH is added to this buffer, the ammonium ion donates a proton to the base to become ammonia and water, therefore neutralizing the base without any dramatic pH change.