Amaterasu is the Sun goddess and is responsible for keeping the balance of nature in the world. She takes the form of a dog, however the catch is she looks like a regular white dog to everyone. Only those pure of heart and chosen are able to see her markings, this is why villagers never react to her presence.
chibitarasu is her son and is a puppy in okami-den.
Okami itself means great diety or wolf depending on how it is used, which is a fitting name for both mother and son.