Early robotic lawn mowers needed a buried wire around the lawn to know where to cut. Newer models use satellite positioning and on-board sensors to map the garden and mow in orderly patterns, removing the awkward installation and letting owners set zones from an app.
Better navigation means tidier results, the ability to handle complex gardens, and obstacle avoidance for pets and toys. They work best on open, reasonably flat lawns, and tall or wet grass still causes trouble, but for routine upkeep they quietly keep a lawn trimmed with little human effort, much as robot vacuums do indoors.