The cell's Golgi apparatus, commonly known as its "post office," is vital for refining, organizing, and enclosing proteins and lipids synthesized in the endoplasmic reticulum (ER). Proteins move from the rough ER to the Golgi, where they are altered, for example, by adding carbohydrate groups (glycosylation). Subsequently, the Golgi sorts and packages these molecules into vesicles for delivery to their intended locations, such as secretion from the cell. The Golgi apparatus's main role is therefore to modify, sort, and package proteins for secretion.