Introductory Review

Abstract

Our current state of understanding of the planetary nebulae (PNe) phenomenon is reviewed in the context of modern stellar evolution and dynamical models. Also discussed are a number of new problems that have emerged as the result of recent space (x-ray, UV, optical, and infrared) observations. The roles of PNe in the chemical (atomic, molecular, and solid-state) enrichment of the galaxy and as tracers of the large scale structure of the Universe are also discussed.