Manual: Regular RC Control, no stabilization, All RC Inputs are passed through to the outputs.
Stabilize: RC Control with simple stabilization, if you let go of the sticks then ArduPlane will level the plane.
Fly By Wire A (FBWA): ArduPlane will hold the roll and pitch specified by the control sticks.
Fly By Wire B (FBWB): ArduPlane is similar to FBWB but will try to hold altitude as well.