So we all know that organelles and cellular materials move about. One way that endocytic traffic occurs is via clathrin-coated vesicles. The clathrin coat, which is made of proteins, interacts through receptors with extracellular molecules that are going to be taken up into the cell. In other words, the clathrin-coats help facilitate endocytosis.
Clathrin-mediated uptake is often known as receptor-mediated endocytosis, because of the interaction with transmembrane receptors.
Eventually, the vesicles shed the clathrin coats and fuse with endosomes. Within the endosome, proteins that are to be recycled are separated from proteins that are going to be kept.