How does a acid buffer work?

For example CH3COOH buffer Buffer is in equilibrium like this - CH3COOH = CH3COO- + H+When a little bit of Acid (H+) is added equilibrium shifts left (as equilibrium shifts in the opposite direction when the concentration of something increases on one side), decreasing the concentration of H+ therefore minimising the change to the pHWhen a little bit of a base (OH-) is added equilibrium shifts right, increasing the concentration of OH- therefore minimising pH change.