Original: They operate more smoothly, quietly, and reliably than other types of compressors in the lower volume range Often, one of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of fluid or gas between the scrolls.
Simplified: They operate more smoothly, quietly, and reliably than other types of compressors. Often, one of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of fluid between the scrolls.