Title II an III of the ADA define a service animal as a dog that is individually trained to perform work or a task to assist a person with a disability in daily life functioning. The work or task must be related to the individual's disability.
Some of the tasks that service dogs perform include:
guiding people who are blind
retrieving items, pushing/opening doors
helping with balance or avoiding falls
alerting to oncoming seizures or change in blood sugar
alerting someone who is deaf
Examples of Tasks
Alerting and protecting a person who is having a seizure.
Calming a person with PTSD during an anxiety attack.
Emotional support animals alleviate the symptoms of a disability or simply by their presence (Fair Housing Act Definition). Animals besides dogs may be considered emotional support animals.
Emotional support animals are not covered by the ADA.