A cmotion joint is the Cartesian driving constraint for a selected translational or rotational degree of freedom of a reference frame. Either of x, y, or z component of the action marker relative to the base marker is constrained by the specified function. Definition of a valid function expression is explained in Function Expression.
Figure 1 CMOTION (Cartesian Motion) icon on Working Window
Figure 2 CMotion icon of the Joint group in the Professional tab