Buffer Solution is a water solvent-based solution consisting of a mixture of a weak acid and its conjugate base of a weak acid, or a mixture of a weak base and a conjugate acid of a weak base. They resist change in pH upon dilution or adding a small amount of acid/alkali to them.
A buffer solution is a solution that can maintain the Hydrogen ion concentration (pH) with only minor changes in dilution or addition of a small amount of acid or base.