What is existentialist philosophy? (As explained by AI)

Existentialist philosophy is a philosophical movement that emerged in the 19th and 20th centuries, primarily in Europe, and is characterized by a focus on individual existence, freedom, choice, and the experience of living. Existentialism is not a unified school of thought with a specific set of doctrines; rather, it encompasses a diverse range of perspectives and approaches. However, several key themes are commonly associated with existentialist philosophy: