What year and trim level is your car? Can you put that in your signature?
The primary purpose is to automatically level the rear of the car when you load up the back seat or the trunk with dead bodies.
The utility inflator is just an added bonus to give the suspension compressor another thing it can do. It'll take awhile to fill a car tire, but it WILL do it. My compressors put out about 70psi, but at low flow rates.
ELC- Electronic Level Control. A sensor on the right rear A-arm of the suspension tells the system when to add or remove air from the rear struts. The rear struts (actually shocks) are GAS, with air assist.