Every Grevit component instance gets one unique GUID when its being created. Once set, the GUID remains like this to identify the element in Revit or AutoCad if you want to update it. There the GUID is stored in a parameter. In some situations you want to avoid saving all the GUIDs in your GH file. If you have many objects for example it can slow down your GH definition. Simply placing the settings component in your GH definition stops saving the GUIDs.