For my Scion tC, I have a ''3'' gear. I know D is drive and R is reverse and N is neutral.. what is ''3'' used fo

its probaly to shift down if you have a 3 then you should also have a 2 and 1

It is a way for you to put an automatic into 3rd gear. 1 = 1st gear 2 = 2nd gear so on. They're mainly used when you are going up a hill.

''3'' is used for going uphill. When in ''3 the engine revs at a higher sound, which results in less fuel economy than D.

You can shift with automatic cars using the 1(L), 2, 3, and D gears.
1 or L is first gear, 2, is 2nd, 3 is 3rd, and D is 4th.
You could also leave it in D and let the car shift for you.
It is still not has fast, reliable, or as light as a manual car because the manual is lighter and has more gears and you can change them yourself.

3 is most likely to lock out overdrive. The ones that say low and L2 are actually 1st and second gear lockouts that lock the gears until you shift. One guy said to pull hills, but you would be suprised how good an automatic takes off in ice and snow in 2nd gear.

Gives more torque for hills and slippery surface ect.