It is used as storage inside of processing setups and can hold up to 256 stacks. It also has an automated output to the side the arrow points and must be provided with a small amount of Energy Units (EU) to function.
By using a Screwdriver on its output, the Superbuffer Buffer can be programmed to output only stacks of certain sizes (e.g., always sending 8 items into a Furnace, so it does not waste Coal). The Super Buffer has no GUI, so it is not possible to see the items it currently holds.
Even though its automated output does not work without energy, other machines can still pull items from the Super Buffer.