Precognition users have the ability to foresee possible futures and observe what may happen. As knowledge of the future invariably causes that future to change, visions of the future are subject to frequent shifting. While not being able to select futures or travel through time, these visions may assist in possible courses of action.
Doomies were ones who could see the future; this ability manifested in degrees from flashes of danger to full-blown visions. In Pilgrimage to Hell, weaker doomies were called "sensers"; later books make no distinction, calling all muties who can sense the future "doomies". Full-fledged doomies are very rare; most people with this power (like Krysty Wroth) have a "danger sense", but not visions.