It is often convenient to treat a collection of objects as a single object. This can be achieved by grouping objects. The result is a geometric object, which can be moved, scaled, rotated etc. as a whole. To edit its parts or to move parts of it with respect to others, however, you have to un-group the object, which decomposes it into its component objects. To un-group a group object, select it, bring up the object menu, and select the Ungroup function.
Group objects can be elements of other groups, so you can create a hierarchy of objects.
A second function of groups is that they allow you to add additional information to an object or group of objects. In particular, group objects allow you to set a clipping path on part of your drawing, to create links to external documents or websites, and to decorate objects. See group objects for details.