Linked from
The 13 pages that link to Vacuum pump, each with the reason it gives.
VacuumRelated: Pumps create low pressure by transferring gas out of the region.
Gas pressureRelated: It creates pressure differences by reducing the number of gas particles.
Vacuum dryingRelated: It removes water vapor and noncondensable gases from the drying chamber.
TorrRelated: Pump performance and attainable vacuum are often reported in torr.