Mustang for racing please read details?
The shifter can be changed, but as the other answer said, it is a shifter which allows you to put the car in first gear (all the way down towards you) and as you accelerate and want to upshift, you just "bump" the shifter handle forward allowing the transmission to ****f into the next higher gear. If it is a 3 speed, then you would "bump" it twice to reach 3rd gear.
Usually these are used for drag racing type setups. You can place it in "drive" (depending on how the tranny was built) and it will shift like a normal automatic.
If you want to show off, then pull the shifter handle all the way down towards you into first gear, mash the gas and bump the shifter foward for the next gear when you reach shifting RPM. Same for the 2nd to 3rd gear shift.
Have fun and don't wreck your car, those are getting expensive and hard to find!