1991 Automatic question

Howdy

I just got a 1991 Integra with an auto, and I was curious about the different modes on the shifter. There is the typical Drive and 2nd gear, but there is also an S mode, which is switchable by a button on the shifter. THis button toggles between S3 and S4. Are these simply 3rd and 4th gear, or are they performance modes.

thanks