Rotary vane pumps have two round, rotating rotors (vanes) inside of a circular cavity. The rotors are offset from each other, creating vane chambers that create a vacuum. The vane drives out the same amount of fluid each rotation, providing an even and deep vacuum.
The two rotors are combined on one pump shaft, and the two stators are combined in the same housing. The shaft of the pump turns the rotors, causing the vanes to brush against the walls of the housing (with centrifugal force), creating a seal that drives the vacuum.