Service Dog/therapy dog
A therapy dog is generally understood to be a canine which is made available to exchange physical contact such as hugs, petting and belly rubs which are widelyk known to develop a euphoria amongst homo sapiens who partake of the contact. Such dogs may be highly trained and certified to negotiate complex environments as often found in hospital environments.
It is important to distinguish such creatures from service dogs which are individually trained to perform a task or work for persons with disabilities in one or more major life area.