A day in the life of a robot vacuum
Picture a robot vacuum starting a cleaning run in an unfamiliar living room. It spins up its LiDAR or camera to start scanning shapes around it, while its wheel encoders begin counting rotations to estimate how far it has traveled. Every fraction of a second, it merges these signals into an updated internal map, plotting where walls, furniture legs, and doorways seem to be relative to its own position.
This isn't a one-time snapshot. The robot rebuilds its picture of the room continuously as it moves, because its own estimate of 'where am I' drifts over time and needs constant correction from fresh sensor data. That's why a robot vacuum sometimes pauses or seems to hesitate near tricky spots like under a couch, it's reconciling ambiguous or missing sensor data before committing to a path.