What is the difference between a therapy dog and a pet dog?

Service dogs perform a service, like guide dogs for the blind or dogs that are trained to assist a wheelchair bound person by retrieving specific items etc. A therapy dog is no different than a pet, only in having it registered as such allows a person to claim their pet provides them with emotional support, usually for mental health issues such as depression, PTSD etc.
Anyone can request their pet be considered a therapy animal, this them allows them access to certain housing just as a service dog is allowed access to public places where pets would normally not be allowed.

I should add that “therapy” animals also are used to visit the elderly in nursing homes, sick kids in hospital, etc. Obviously they need to be calm and good natured to qualify for these types of activities.

Therapy animals are very acclimated to being with people of all sorts, in all kinds of conditions, and extremely not likely to bite.

The hourly rate.

I should look into that exact thing. I have a kid with some issues. I wonder if he qualifies for a therapy dog. It may sound cheap of me, but if I can get the state to cover some of the costs, it would certainly encourage me to make the leap. Pets are crazy expensive here, and vet costs are so enormous, people take ‘health insurance’ for their pets.

@Coloma gives a good description of legitimate service animals.

In some places the difference between a service animal and a pet is mostly the character at the other end of the leash. Because it is easy to get a “certification” for a pet, plenty of people abuse the privileges afforded legitimate service animals and haul their stupid stinking fluffy everywhere including restaurants and food stores.

The difference is about ten grand.