The bounding box is defined as the smallest rectangle, with horizontal and vertical sides, that completely surrounds an object. Bounding box extents are indicated by a hatched box surrounding the object. All coordinates of the object fall within the bounding box. Red dots appear on the selected object(s).
Selection of objects is based on the "bounding box" of the object. When you select an object with the mouse, you must be within the limits of the objects bounding box.
If multiple objects are selected by holding down the SHIFT key and clicking on the object, a dashed line surrounds all the selected objects.