What is the difference between Digital Scroll Compressor and Inverter scroll compressor?

In digital scroll compressors, the motor runs continuously at full speed, and the capacity of the compressor is adjusted by a digitally controlled mechanical unloader (slide bar) which adjusts the vertical positioning of the orbital scroll with respect to the fixed scroll thereby reducing its capacity.

In inverter scroll compressors, the relative positions of the scrolls does not change, but the speed of the motor is adjusted by a variable speed drive, which adjusts the capacity.

The inverter scroll compressor is more energy efficient at part load conditions than a comparable digital scroll compressor. The digital scroll compressor will more closely match a specified load, but is not as energy efficient as a comparable inverter driven compressor. Both types of compressors have associated built-in mechanisms to maintain compressor lubrication at low flow.