A service dog/animal is a specific category. Companion dogs, emotional care dogs, etc., do not have the right of access to all places that a person can go. In some states, there are access regulations for housing, companion dogs must be allowed even though the property has a no pet rule. I think that the dog owner has to provide proof of actual need from a doctor.

There are quite a few different kinds of service animals - guide dogs, seizure dogs, dogs that serve a hearing impaired handler, dogs that pull a wheelchair, and many other services that they might provide.

There is no mandatory certification for service animals, so that makes it very easy for anyone to claim that their animal is a legitimate service animal. It's an unfortunate situation because it makes people suspicious of the validity of true service animals.

Some types of service dogs are appropriately handler trained, while others need professional training. It's a situation with too many gray areas, for sure.