Snapping (Constraints). The constraints must be used if you want to snap to an object or use the smart points.
I find some of the constraints troublesome, and I find some to be useful. For example, I never use the Snap to Grid, but on the odd occasion I turn on the smart edge or the tangent snaps. If you turn all the constraints on, you will find Vectorworks gives you too many options, too many snaps and helpful guide lines.