There are two kinds of buffer
a) acidic buffer
b) basic buffer
They both resist change in pH on addition of small amount of strong acid or base
as asked in question we will consider addition strong acid that is [H+]
a) acidic buffer: it is a mixture of weak acid and its salt with strong base
say CH3COOH + CH3COO-Na+
When we add H+, the H+ are being consumed by acetate ions to give acetic acid
CH3COO- + H+ ---> CH3COOH
So it accepts H+
b)basic buffer
Example: NH4OH + NH4Cl
when we add H+ , the OH- will react with it to form water
So it accepts H+