When reading and writing network list objects, you may wish to modify its top-level members rather than its complete list of elements, or other extraneous metadata. The API offers two query parameters, includeElements and extended to speed up GET requests for this top-level data, and to speed up responses that reflect requested changes. When you set includeElements to false, you don't get the full list of elements. When you set extended to false, you don't get data about activation status or the object's creation and latest modification.
Whenever you run the Update a network list operation, you have the option to PUT back this smaller object, omitting many data members from your request, such as the list of elements, without affecting corresponding values.