Some camping areas, notably LTVAs, require RVs to be “self-contained.” This example is from the BLM supplementary rules for LTVAs:
Self-contained camping units must have a permanent, affixed waste water holding tank of 10-gallon minimum capacity. BLM does not consider port-a-potty systems, systems that utilize portable holding tanks, or permanent holding tanks of less than 10-gallon capacity, to be self-contained.1)
Other requirements may be:
Exceptions may be:
Sometimes “self-contained” also means something like “livable space” for purposes of qualifying as an RV. In this case it can also involve: