  Insights are often considered the ideal outcome of visual analysis sessions.
However, there is no single definition of what an insight is. Some scholars
define insights as correlations, while others define them as hypotheses or aha
moments. This lack of a clear definition can make it difficult to build
visualization tools that effectively support insight discovery. In this paper,
we contribute a comprehensive literature review that maps the landscape of
existing insight definitions. We summarize key themes regarding how insight is
defined, with the goal of helping readers identify which definitions of insight
align closely with their research and tool development goals. Based on our
review, we also suggest interesting research directions, such as synthesizing a
unified formalism for insight and connecting theories of insight to other
critical concepts in visualization research.
