Thank you.
Service dogs are working animals. They're not pets. Service dogs are trained to perform tasks for people with disabilities. Guide dogs assist with navigation for people with diminished vision. Hearing dogs alert people with hearing impairments to sounds like a doorbell. Mobility dogs retrieve objects or pull wheelchairs. Mental health service dogs calm individuals, generally speaking, to avoid or defuse a triggered episode.
In contrast, emotional support dogs can be considered pets. They are typically not trained to perform tasks that directly relate to a disability but are considered to provide therapeutic benefit through companionship and affection.
There's a third category of dogs there, too: therapy dogs. I'll just bring this in for completeness. Those dogs are not owned by patients but are present during the delivery of treatment. They are not service dogs and are distinct from emotional support dogs, which are primarily for the benefit of their owner.