Control Points are the dots in the corners of a selected object which can be used to Edit it.
Control Points in Trace are displayed as colored Dots on the Segments that make up the Object. Beginning/End Points are Blue and Center Points are Green. These can be toggled on/off in the Options menu.
Moving these Control Points will change the shape of the element being moved.
Control Points on Bounding Rectangle are displayed as darker dots on the corners of the Bounding Rectangle of the selected Object that can be used to edit the object.
See: Bounding Rectangle Definition