Buffer solution is a solution whose....???

pH of the solution generally changes on addition of small amount of acid or an base to it.But a buffer solution is an solution which resist the change in pH on addition of-
1.small amount of an acid
2.small amount of an base
Depending on pH values buffer soution are of two types-
a).Acidic Buffer-when pH is less than 7
b).Basic Buffer-when pH is more than 7