A buffer system is a solution that prevents the drastic change in the concentration of H+ ions (and pH) in the system. It is useful in the biological system because proteins and enzymes are highly susceptible to degradation and denaturation at any time if there is a change in pH. A buffer solution consists of two components; weak base and its conjugate acid.
For example, there are many types of buffer systems in our bodies. These are ammonia buffer systems (composed of ammonia and ammonium ions), bicarbonate buffer system (composed of bicarbonate ion and carbon dioxide), and many others involved in amino acids and peptides. A buffer solution is also important for the protein and enzyme work in the biochemistry laboratory, where researchers used it for the extraction of proteins/enzymes and their storage without letting them degrade.
If there is an increase in pH, the acidic component of the buffer solution will neutralize the OH- ions if there is a decrease in pH the basic component of the buffer solution will neutralize the H+ ions. In this way, the buffer system prevents the drastic change in the pH of the solution. However, every buffer system has its own buffering zone, beyond that they will not work. This is because, out of the buffering zone or range, there will be no acidic or basic components left to neutralize the H+ or OH- ions.
Every buffer system is measured by its ionic strength and pH value. As, for example, 50 mM phosphate buffer of pH 6.8 where 50 mM is the ionic strength of the phosphate buffer and 6.8 is the working pH of that buffer and its buffering zone will be 6.8± 1. That means the phosphate buffer of pH 6.8 can work well within the range of pH 5.8 to pH 7.8. I hope it is clear for you now the importance of a buffer system.