The transform center, or pivot point, is the location about which a rotation takes place, or to and from which a scale occurs. All nodes in 3ds Max have a pivot point. You can think of the pivot point as representing a node's local center and local coordinate system.
The pivot point of a node is used for a number of purposes:
The thing that most users think of as the pivot point -- graphically represented in 3ds Max by the axis tripod that is displayed when a node is selected and the coordinate system is set to local -- is actually just a visual representation of the node's transformation matrix.