Does anybody know the technical difference between "4WD auto" and "4WD lock" on the Ram 1500 2010? Is there a middle diff on the ram and is open in AWD auto and it locked in 4WD lock?

 

4wd Auto is like all wheel drive. It has a clutch design in the transfer case that allows slippage so that it won't bind up on dry pavement. It is for use on mixed terrain such as partially snow covered roads, etc. 4wd lock is like a std 4wd for slick surfaces only and has the front and rear locked together.
2wd is recommended for normal driving because it disengages the front differential and reduces drag and helps mpg.
Your transfer case has the best of both worlds with the 4wd auto option.