In a variety of eukaryotic cells, autophagy sequesters a portion of the cytoplasm and targets it to a lytic compartment for degradation in bulk. Autophagy is a dynamic process for degrading cytoplasmic cargoes with various degrees of selectivity, and its activity is tightly regulated in a nutrient- and development-dependent manner. Autophagy research has drawn much attention since autophagy not only is an interesting cell biological phenomenon but also has great potential for medical and agricultural applications. For example, autophagy is associated with cancers and neurodegenerative diseases in human and mammalian cells and is also suggested in remobilization of nutrients during the senescence of plant leaves. In this general review, we describe genetic components of the core autophagic machinery conserved among yeast, animals, and plants and briefly explain how these components are responsible for major steps in plant autophagy. We discuss four common features of autophagic processes: (i) autophagy as a degradation pathway, (ii) the concept of flux in autophagy research, (iii) dependency on developmental and nutritional cues, and (iv) diversity of autophagy, focusing on selective types of autophagy. We also summarize cell biological and physiological functions of plant autophagy. Our intention is to provide a quick guide to autophagy for those who are new to autophagy research.