What do the number 2 and 1 mean in the 1987 Chevy S-10 Gearshift.and the D with a circle is for driving on the freeway right?

What do the number 2 and 1 mean in the 1987 Chevy S-10 Gearshift.and the D with a circle is for driving on the freeway right?
The "2" means that the transmission will only shift up to 2nd gear and will just rev the motor higher the faster you go. The D with a circle means Overdrive. And yes this is what you use for any normal driving.