About grouping drawing objects
When you group drawing objects, you combine them so you can work with them as though they were a single object. You can flip, rotate, and resize or scale all objects in a group as a single unit. You can also change the attributes of all objects in a group at one time — for example, you might change the fill color for or add a shadow to all objects in the group. You can also build complex drawings by creating groups within groups. You can ungroup or regroup a group of objects at any time