Technically speaking, pasteurization is rendering eliminate some percentage of bacteria via temperature and time. With a pot you can boil milk, which will render it safe for a time, and also destroy a lot of nutrients and change the flavor. Pasteurization as done in a dairy is typically lower temperature for a longer time, keeping the flavor and nutrients intact.

Because it’s not fully boiling you typically want a sealed container to keep new bacteria from getting in during the process. A pressure cooker is fine enough for home use.