Your map app draws a crisp little dot and a tidy circle, and the circle is the honest part. That circle is the app admitting the truth is somewhere in here. Understanding what widens or tightens it tells you almost everything about real-world positioning.
On a clear day with open sky, a modern phone using several constellations lands within about three to five metres. Good enough to know which side of the street you are on, not always enough to tell your balcony from your neighbour's. Survey gear using correction signals can reach centimetres, but that is specialist equipment, not the phone in your pocket.
Then the sky gets complicated. Tall buildings bounce signals so they arrive late, a gremlin called multipath that can throw your dot across a plaza. Dense trees, tunnels, and underground stations block satellites outright. Even the ionosphere, puffed up by solar weather, subtly delays signals and smears the fix. This is why your dot sometimes sprints down the wrong road before snapping back.
Indoors, pure satellite positioning mostly gives up, so phones lean on wifi and cell signals to guess. That guess can be excellent in a mapped city and comically wrong in a new building, which is why you occasionally arrive, digitally, three floors underground. Our GPS versus GSM piece explains that fallback.
The reason this matters beyond trivia: anyone promising to pin a specific phone to a specific chair from a website is promising something the physics does not allow, even under ideal conditions and even with your cooperation. Real accuracy is a fuzzy circle, not a crosshair. On Live Sat Tracker the crosshair is a joke, the circle is imaginary, and nothing you enter is measured at all. See how we fake the precision for the cheerful details.