Kensho means "seeing nature", that is, seeing one's own true nature. The term is used especially in Rinzai Zen for a first, often brief, experience of insight.
Kensho and satori are frequently used to mean the same thing. Where a distinction is made, kensho tends to refer to an initial glimpse and satori to a deeper or more lasting realization.
In Rinzai training, a kensho experience is traditionally followed by years of further koan study, on the view that a glimpse needs to be clarified and matured.