Autophagy is a catabolic process of the degradation of cellular components by lysosomal enzymes. It is essential for cellular homeostasis by maintaining the balance between the synthesis, degradation and turnover of intracellular constituents. Its primary role is cytoprotective. It protects the cells against the accumulation of damaged organelles or protein aggregates and it ensures cell survival in extreme conditions like during starvation or oxidative stres. Three major forms of autophagy are known: chaperone-mediated autophagy, microautophagy and macroautophagy. In macroautophagy, long-lived proteins, organels and even specific nuclear regions could be eliminated. In this paper, macroautophagy is mostly in focus. Many human diseases like muscular disorders and neurodegenerative disorders appear as a consequence of autophagic malfunctioning. Excessive autophagy is cell-destructive and could lead even into autophagic (type II) programmed cell death. Autophagy participates also in cell defense against infectious disease. Autophagy has special role in cancer, where activated or inactivated benefit tumoral cells in different stages of cancer. New discoveries about mechanisms and regulation of autophagy would enable scientists to develop in future new methods for manipulating the activity of the autophagic pathway as new therapeutic tools against some diseases, particularly muscular disorders, neurodegenerative disorders and cancer.