Not a silly question at all. You have a Borg Warner automatic. When placed in D1, your trans will upshift from 1st to 2nd to direct drive from a dead stop. In D2 position, the trans will start out in 2nd and then up to direct drive. This position is meant to be used around town on flat surface streets or in slippery conditions. L position is "lock". It will hold first gear for engine braking down a grade, or it can be selected when the trans is in 2nd gear and it will hold that gear and not upshift.