It comes in two modes: Automatic, or Tapshift.
Like any automatic you can put it in reverse, drive and neutral etc. You can also put it in Tapshift mode (whatever GM calls it) and you control the gears like you would in a manual transmission(kinda). You can shift up and you can shift down. Tap the right lever and it goes to the next gear, tap the left one and it goes to the previous one.
My understanding of the Camaro tapshift is that you have complete control of UP-shifting, meaning you can go from 1st to 2nd ONLY when you tap Up-shift. When Down-shifting, you can control it to an extent... after it goes down to a certain RPM it will automatically down shift to the previous gear for you. That doesn't mean that you CAN'T down shift yourself, it just means that once it reaches whatever RPM threshold it has, it will down-shift it for you.
It might seem complicated but it really isn't.
Tap right = Up-shift
Tap left = Down-shift
Complete control of up-shift
Limited control of down-shift
Or just leave it in D to drive it like a normal automatic.