A part (except the UNIVERSE) always has an ordinary parent. If a part is the most distal segment (= the "goal") of an IK-chain which is curently set "on", it also has an IK-parent alias inkyParent. By default the inkyParent is that model's BODY, but it can be changed, by the "Object" dropdown menu. IK = Inverted Kinematics. IK-parenting is used to make closed loops of jointed parts, e.g. my diver models' breathing tubes, or a man holding a tool or weapon in both hands.