Axis systems and planes are coordinate systems that you use to orient your machine and parts. There are several types.
Axis System
A coordinate reference system very similar to the rosette concept in TruPlan.
Tool Change Point
An axis system that defines where you want the machine to go when you want to change the roller.
Home Point
An axis system that defines where the machine starts working from; that is the starting point of the tool path.
Plane
A reference coordinate system similar to an axis system. A plane has three values: Origin, Direction 1, and Direction 2.
Safety Plane
A plane that defines a location where you can move the machine, specifically its head, to a position that is considered safe from collisions. This is normally far away from the workpiece or the part that you're machining, either very high above the part or far to the left or right of it.