definition of buffer solution and buffer capacity type of buffer solution and its example

the solutions in which the addition of small amount of acid or base not change the pH such kind of solution are called buffer solution .

hence buffers are the solution with reversed acidity and alkaline alkylinity .
buffer solution usually consist of 
1 .weak acid and its salt :
acetic acid + sodium acetate 

2. alkaline mixture of weak base and its salt :
ammonium hydroxide and ammonium chloride
3. weak acid and weak base: ammonium acetate

buffer capacity 

buffer action is defined as the resistance to change in the h+ ion concentration on the addition of acid or alkali .

the magnitude of the buffer action of a buffer is determined by its buffer capacity it may be defined in terms of addition of both acid and alkali.
 usually it is measured by the amount of strong base required to produce unit change of the PH in the solution.