A playback buffer holds some media ahead of the point currently being shown. It gives the player material to continue presenting during short delivery variations. Buffer size or duration involves trade-offs, including startup time and distance behind a live event; it cannot compensate indefinitely for delivery slower than the programme's ongoing data requirements.
A practical example
A player can continue showing a few seconds of a programme while the connection briefly slows. If fresh media does not arrive before that stored content is used, playback pauses while the player obtains enough additional data to continue.
A common misunderstanding
A larger buffer cannot fix an unavailable stream or guarantee uninterrupted viewing. It can also increase delay behind a live programme, so compare supported settings against the actual problem being observed.
Related terms
Stable technical definition. Editorial approach