:shock: You're going to have to be more specific. Are we talking about a data buffer, a buffer circuit, or the white fuzzy thing attached to a motor used for polishing cars? :roll:
Buffers are interposed between a source and a load that the source is not able to drive directly, i.e., when more current is required than the source can provide. You could call this impedance matching in a general sense. The more common meaning of "impedance matching" is to create a source impedance that equals the load impedance, in order to provide maximum power transfer, minimize reflections on transmission lines, etc.