A buffer is something that prevents something else from being harmed or that prevents two things from harming each other.

If something is buffered, it is protected from harm.

The buffers on a train or at the end of a railway line are two metal discs on springs that reduce the shock when a train hits them.

A buffer is an area in a computer's memory where information can be stored for a short time.

If you say that someone, usually a man, is an old buffer, you mean that you think they are rather foolish.