l drive a mitsubishi montero sport 4WD automatic on the shifter there is the R=Reverse D=Drive N=Neutral... my question is... what is the 3,2,1 for? Is there any place online that l can read about this info? l can not find anything! l know they are just other gears but when are they to be used?

They r simply allowing u manual control over ur automatic transmission. The vehicle will stay in the gear u select. Of course it wo not let u overrev, so if u select a gear that the computer deems too low it will wait until u slow down. Also, if u start out in a gear that is too high, it will shift as if u r in ''D'' until it reaches that gear & then stay in that gear. You really need not worry about using them as the vehicle will select the appropriate gear for you.

The various sensors in the vehicle
will select the appropriate gear for u in the ''D'' position.

as to ur Question - when to use them?

general situations would include :

*driving up long hills / mountains -
if u feel the need to have a bit more power -
(you may not really go faster due to the RPM limit sensors)
or down long hills / mountains -
if u wanted the engine to do some of the braking
(the RPM limit sensors may not allow this)

*Towing

*Off-road driving

*when u want to burn More gas*
The various sensors r intended to provide optimum performance for given situations. You have choices.