Older automated carts followed fixed wires or markers and could not deviate. Autonomous mobile robots carry their own sensors and maps, so they plan routes, avoid people and obstacles, and adapt when the layout changes, without rebuilding the floor around them.
They coordinate so many robots can share the same space without collision or gridlock. This flexibility is why they spread quickly through storage and fulfilment work, where the layout and the flow of goods change far too often for fixed paths to keep up.