The option automatic curve is the only strategy where the curve is calculated automatically by the system for each contour and the user should not pass any tilting curve geometry. The automatically generated curve tries to dampen the tool motion by a user given dampening distance. This type of tilting is helpful e.g. for cutting deep cavities. Here the fixed tilt angle applies and is defined as the angle from z axis towards the internal calculated automatic curve at each point of the tool motion.
In the picture you can see the drive surface and compared to that the automatic curve. The Curve is similar to the shape of the drive surface. In the indent the curve is much smoother than the actual drive surface though.