In point/edge/face mode, the tool changes only selected areas. In object mode, the whole object is considered.
The tool has the following controls:
Angle - the threshold angle. In edge crease creation, surrounding faces must exceed the limit angle at both ends of the connecting edge. A sharp point crease is set when all faces connect to the point's average normal with an angle that is greater than the limit. For example, a cone like surface usually gets a point crease in the apex, although surrounding cone side faces join to each other smoothly. That happens because each face has a sharp angle with the apex direction.
Target - selects if point, edge or both crease types should be considered. Often the threshold angle shoudl be different for edge and point creases.