There are several types of navigation in total. You can find more details about them in this article
. In short, some robots create a map of the room, and some do not. But don't rush to run for a vacuum cleaner with a mapper! They cost more but are not suitable for all rooms. For example, for apartments of up to 60 square meters, you do not need a mapper, because the robot vacuum cleaner will go around everything more than once during its work. For large apartments and country houses, robots with mapping are recommended. There are different variations of a mapper, you can find more info about it in the article at the link above.