Vipassana is a Pali word which means: Seeing clearly, seeing specially or seeing through (Vi – clearly, specially, into, through + passana – seeing). Vipassana means introspection, intuitive wisdom, intuitive knowledge. Vipassana is often translated as Insight.
Seeing what clearly? Insight into what?
Vipassana means seeing through the true nature of reality or Insight into the true nature of reality. It means seeing things as they truly are. Vipassana is the direct and intuitive understanding of the true nature of all mental an physical phenomena.
Vipassana is intuitive knowledge or Insight into the true nature of Nama (mind: consciousness, mentality) and Rupa (body: materiality, physical form) which make up the Five Aggregates of Existence (Panca Khanda: Rupa (body, physical form), Vedana (feeling), Sanna (memory, perception), Sankhara (mental formations, volition), Vinnana (consciousness).)
Vipassana is the realization that all mental and physical phenomena are Impermanent (Anicca), Suffering (Dukkha) and Non-self (Anatta). These three Characteristics of all Phenomena (Tilakkhana) are the marks of Insight wisdom and are the main objects of Vipassana Meditation.
Vipassana is the direct realization of the true nature of Nama and Rupa. All condition whether internal or external, mental or material are Impermanent, Suffering and Non-Self (Anicca, Dukkha, Anatta).
The meditator who develops Insight Knowledge (Vipassana nana) will realize that everything inside oneself and in the world outside of oneself is constantly changing, uncertain or Impermanent; is stressful, dissatisfactory or Suffering; and is uncontrollable, devoid of substance, not belonging to oneself, or Non-Self. These Three Characteristics are the True Nature of all phenomena.