Groups are simply boxes that help you organize your graph.
To create a group, select an area on the graph while holding the Ctrl key, or Cmd on Mac.
You can give each group a title that will be legible even when zoomed out.
You can select all items in a group by double-clicking its header.
When using the Unity control scheme, you can move the group without moving its contents by holding the Alt key and dragging its header.