Q: What do the numbers and letters mean on an automatic transmission: 1, 2, D, L, S, etc?
A: That’s what’s known in the automotive world as the “prindle,” the pronunciation that engineers bestowed on the transmission gear selector because it commonly contained the letters PRNDL for Park, Reverse, Neutral, Drive and Low.
Drive, of course, covers all the forward gears, and because an automatic transmission selects those gears automatically based on throttle position, vehicle speed and other factors, that’s the only transmission position most people select for forward progress.
Most automatic transmissions also allow you to manually select one or more lower gears, such as Low (L), 1st (1) and 2nd (2). In the case of L and 1, the transmission will stay in the lowest gear and not shift on its own. That allows maximum power when you need it, such as on a steep hill, but greatly limits your speed. Some automatic transmissions will shift out of 1st once you reach a certain speed, such as 30 mph, to prevent damage to the transmission or engine, or cut power to the engine. And with others, if you select 2, the transmission starts in 2nd gear and is locked in that gear. This is useful when starting out on slippery surfaces or for engine braking when descending a steep hill.
You also mentioned S, which could be a Sport setting in which the transmission downshifts sooner when you open the throttle to pass and holds lower gears longer for sustained acceleration.
See the vehicle’s owner’s manual for more info. You might be enlightened about other ways to maximize performance or reduce stress on the transmission.