Shrinathji is a form of Lord Krishna manifest as a child with dark complexion. He is shown with one arm raised to represent His lifting of the Govardhan hill to act as a shelter for the protection of his devotees.
The principal shrine of Shrinathji is situated at the temple town of Nathdwara, near Udaipur, Rajasthan.
Nath means 'lord', 'protector' or 'refuge'. Shri and ji are honorific terms added to the names of deities or highly respected people.