Degree of Freedom Control
The Degree of Freedom (relative to the working frame axes) controls across the top of the Minimize Relationships Dialog offer the ability to restrict motion in one axis or another with respect to the working frame, controlling the motion that is allowed.
Selecting X, Y or Z allow translation along these axes while un-checking the boxes prevents the solver from moving in that direction.
The Rx, Ry, Rz control rotation in the same manner. Un-checking a box prevents rotation about that axis.
The rotation centroid controls can be helpful if the working frame is very far from the part. In such a case the optimization process can be slowed due to inaccuracies caused by this rotation point. Selecting Rotate about Centroid allows the fit process to rotate about an adjusted local axis but the Degree of Freedom reference controls are unaffected by this selection.