A scroll compressor actually consists of two scrolls or spirals. One scroll is moving, whereas the second one is fixed (attached to the compressor body). The first scroll orbits (rotates) in a path defined by its mating fixed scroll. The orbiting scroll is connected to the compressor's crankshaft.
As a result of the scroll's movement, gas pockets are formed between the two scrolls. At the outer part of the scrolls, the pockets suck in gas and then move towards the center of the scroll, where the compressed gas is discharged. As the gas moves into the continuously smaller internal pockets, both its temperature and pressure are increased. Thus a desirable discharge pressure is achieved by the motion of the compressor scrolls.
