How does GPS work?

You ask: How GPS find Caveman?

Many small star-things circle earth, way up high — sky tribe call them satellites. Each one shout all day: "Me here, and time now is this." Shout travel as radio wave, fast as light — light run seven times around whole earth in one heartbeat — but still take small moment to reach Caveman. Caveman phone hear shout, check how late shout arrive. Late shout mean far satellite; quick shout mean near. Know distance to one satellite, Caveman could be anywhere on big circle. Know distance to four satellites, circles cross at one spot only — that spot is Caveman. Satellites carry very true clocks, atom clocks, because light so fast, tiny time mistake mean big place mistake. And hear this — satellites never hear Caveman. Phone only listen, then do counting itself. Cave wisdom: GPS not watch Caveman. Caveman phone hear four sky voices and figure out where Caveman stand.