As mentioned, the left one does your front derailleur. If it has 2 sprockets, then yes, all the way forward will be low tension, and drop the chain to the small sprocket and be easiest to pedal.

All the way back will pull the chain to the large sprocket, and be the hardest to pedal.

If there is a third sprocket, then you may choose an intermediate spot for that one.

If you're cross-chained, then you may experience some chain rub, and adjust your derailleur appropriately to eliminate the chain rub. This is why not every stop has a "click".

As also mentioned above, the right one is for the rear derailleur. All the way forward will be a loose cable, and should drop you into the smallest rear sprocket, or hardest gear. Pull it back, and you should incrementally shift to the rest of the sprockets.