Very simple.
Curves are the translation from real head-movements
In (Y-axis) to output movements
Out (X-axis) in degrees.
For Example:
The
Roll translation curve with 40° head-movement gives you 120° output-movement for the skull in the skull-window.
Now, with right-click on curves you can choose predefined curves. And here is what they does:
Yaw is linear
Pitch is 1:1
Roll is large deadzone
Depending on game movements you need and sensitivity in game you can set up every movement independent.
For flight sims try to begin with a curve with medium deadzone and push the curves end up to 180° (red flash), otherwise you can't turn around completely to watch your six.
A deadzone is very useful for a stable view in base position.