How is this different from older guided-vehicle systems?

Traditional AGVs follow a fixed physical path — wires embedded in the floor, magnetic tape, or reflectors the vehicle tracks. If the layout changes, the guidance infrastructure has to change with it.

What does an AMR use instead?

AMRs use onboard scanners and sensors to build a map of their surroundings and plan their own route to a destination, rerouting around obstacles in real time rather than stopping and waiting for a fixed path to clear.

Why does this matter for a warehouse or production floor?

It means the same fleet can adapt as layouts change, without needing floor infrastructure reinstalled — see AMR vs AGV: What's the Difference? for the fuller comparison.