these buttons put your vehicle in high range and low range 4 wheel drive check your owners manual or over the drivers sun visor for more information
---Auto-- means that you have wheel sensors that sense the speed each wheel is rotating, under normal driving the sensors are mostly similar with variance in turning and etc but if a wheel starts spinning out of range than it automatically kicks the front diff on and therefore you AUTOmatically have 4wd, so say goodbye to drifting the corners in 2wd :)