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.
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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.
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See: Bounding Rectangle Definition