What does the TRAC button do and or mean on the dashboard of Saturn 2002?

It turns off your traction control. Meaning the wheels may slip in poor traction conditions when in the on position the vehicles comp. will lessen the torque on the wheels or divert the power to a different wheel. I'd leave it on!

There is also a traction control light that flickers when the traction control is detecting wheel slippage and trying to compensate. I check this and if it flickers too much, I shift down. If you turn off the traction control this light will not flicker, so you won't realize you should shift down.

There are a few rare circumstances where it is useful to turn off the traction control, the button is there for those cases but right now I don't recall them.