Endocytosis is a biological process through which cells engulf external substances and then absorb them by placing them inside the cell. There are several synonyms for endocytosis that you can use, such as: phagocytosis, pinocytosis, receptor-mediated endocytosis, fluid-phase endocytosis, and clathrin-mediated endocytosis. Phagocytosis and pinocytosis are the two most basic types of endocytosis. Similarly, receptor-mediated endocytosis involves binding of ligands to specific receptors and then absorption of the cargo-ligand complex.