When you group 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 or add a shadow to all objects in the group. Or, you can select an item within a group and apply an attribute, without ungrouping. You can also create groups within groups to help you build complex drawings.
You can ungroup a group of objects at any time and then regroup them later.