You can find the chamfering operation in almost all the milling machining.
It's used to create a chamfer on the material with a tapered tool.
Chamfer Depth : It's the dimension of the desidered chamfer
Step Count : Sometimes it's preferable create the chamfer with multiple passes, with this property you decide how passes you need. The tool depths are calculated keeping constant the volume of removed material .
Additional tool depth : This property allow to move the tool down in Z- direction , but keeping the same chamfer depth .
Useful if you want to move the contact point away from tool tip.