A stuff sack is a type of drawstring bag, usually used for storing camping items. Stuff sacks may be used to collect many small items together, just so that they do not become lost. Their most important use is the storage of sleeping bags, which are otherwise very bulky and virtually unmanageable.
The compression sack is a special type of stuff sack, designed particularly for the storage of bulky sleeping bags in internal-frame backpacks. It is equipped with a cloth lid that is attached to the opposite (sealed) end of the sack by adjustable straps. When the straps are forcibly shortened, the sack and its contents are reduced in size.