An RTLS is a real-time location system. A small radio tag is put on a person or a thing, and the system keeps telling you where that tag is, right now — usually inside a building. Hospitals use it to find equipment; warehouses use it to find boxes; some workplaces use it to see where staff are on a site. It is not the same as the GPS in your phone. GPS uses satellites and works best outdoors; an RTLS usually uses indoor readers and tags stuck on what you want to follow. The name is technical — engineers, hospitals, and factories say it. You say the letters: R-T-L-S.