So I'm not a genious. i used to drive a stick and have also had automatics all of my life. i've never been quite sure why autos have gears 2 and 1 after D. what do we need them for. also, what exactly does overdrive do. :?: :?: :?: :?:

Overdrive really lowers the engine speed while cruising (it is best noticed on the interstate). Gears 1 and 2 are very low speed gears and should only be used when driving slowly in snow or mud.