How is a vesicle formed during endocytosis?
In clathrin-dependent endocytosis, clathrin molecules will assemble and form a cage structure that forms coating around receptor with substrate thereby engulfing it.
TZOVINAR M. have given an answer for pinocytosis. The substrate that gets engulfed by the cell through pinocytosis is non-specific. There is also receptor-mediated endocytosis such as clathrin-mediated entry