Lord Dhanwantari, is one of the Avatar of Lord Bishnu who emerged from Kheer Sagar ( Ocean ) as scripted in Bhagabata Purana. Dhanteras is the day, Lord Dhanwantari is commonly known as physician of Devas. Every mortal beings seek the blessing of Lord Dhanwantari for good health and long life.
Dhanteras day is the appearance day of Lord Dhanwantari, he appeared with the pot of amrita (nectar) during the story of the Samudra (or) Sagara Mathana whilst the ocean was being churned by the Devas and Asuras. Dhanvantari is depicted as Vishnu with four hands, holding Shankha, Chakra, Jalauka (leech) and a pot containing rejuvenating nectar called amrita. He is often shown with a leech in his hand rather than the scriptures.