When using presence detection for lighting control, there are two basic initial statuses that need to be distinguished: Presence status and absence status.
Typical motion detectors (see footnote) installed on buildings are tasked with registering approaching persons reliably and switching on the light. Where they are installed on front doors, they are usually intended to keep the light switched on for as long as the person lingers in the entrance area. The aim is to provide protection against break-ins and accident risks by avoiding darkness.
In contrast, an indoor light management system’s presence detection facility has the (main) task of reliably turning off the light once no more persons are present in the room – and only then. Inasmuch, one could also call this feature "absence detection". Energy is only saved in cases of absence, which is the installation’s intended purpose (see also chapter 184.108.40.206 "Light and the environment").
In the following, the indoor purpose – meaning "absence detection" – and its many implementation constellations are addressed.