Kensho, literally seeing nature, and satori, literally understanding or comprehension, are the two terms Zen Buddhism uses for a direct, non conceptual glimpse of one's own Buddha nature, the sudden recognition, described across the tradition as immediate rather than reasoned toward, that the sense of a separate, fixed self is not the final truth of experience. The two words are often used loosely as synonyms in general English writing about Zen, but within the tradition itself they are usually distinguished by depth and stability: kensho names an initial, often brief opening, a first genuine glimpse that can occur relatively early in practice, while satori is generally reserved for a deeper, more thoroughgoing and lasting realization, sometimes described as the kind of breakthrough associated with a teacher's formal recognition of a student's attainment.
Zen literature is famously resistant to describing the content of these experiences in positive terms, consistent with the tradition's broader distrust of concepts as a route to what it considers the deepest realization, preferring instead paradoxical stories, koans, and direct pointing between teacher and student over doctrinal description.