A cell is separated from its environment by the plasma membrane through which it accepts signals and nutrients. The plasma membrane also allows cellular response to them. Endocytosis has a key role in these processes. It provides and regulates many cellular processes, including cell signalling, cell polarity establishment, cell growth and differentiation. Many entry pathways into cells have been identified, which differ in terms of different types of cargo internalized and specific molecules that allow the endocytic process. The endocytic pathway starts with the selection of cargo at the cell surface, and is followed by invagination of plasma membrane and formation of endocytic vesicles. These vesicles, through interactions with other cellular compartments, deliver its cargo and membrane proteins to different locations in the cell or recycle them back to the plasma membrane and the extracellular matrix. Endocytic pathways can be used for drug delivery for therapeutic purposes, but unfortunately they are also exploited by pathogens to enter the cells. Changes in endocytic pathways may be the reason for many diseases and their understanding is therefore important for effective treatment of these diseases. In this review article, we have gathered known facts about different types of endocytosis and endocytic pathways. We also discuss their role in the development of diseases and treatments.