Picture from: http://www.technorms.com/
You can set up switch control to choose from 4 switches - turning head left and turning head right (uses the internal camera), an external Bluetooth switch, or touching anywhere on the screen (for those who cannot isolate and target one spot). Note: using the full screen makes it hard to turn off switch control with touch. If this happens turn on Siri request it to activate assistive touch. This turns off switch control.
Each of these methods can be set up to do a variety of actions, such as select (tap), go to Home screen, increasing or decreasing volume, activating Siri, etc. All of these options are listed under each switch set-up in the Settings app.
Another feature is Point Scanning which is using cross hairs to pick a specific screen location. A popup menu appears at the pinpointed location for more choices. One drawback, the iPad has to be positioned carefully to ensure the camera can see your face, or you will get a message at the top of the screen saying that it cannot. Just adjust the angle a bit and it should work. Mounting or having a stand to keep it steady is recommended.
For more information go here.