These terms are often used interchangeably but have different legal standing and requirements.
Service dogs
Individually trained to perform specific tasks related to a disability, with broad public access rights under the ADA.
Emotional support animals
Provide comfort through their presence, without specific task training, and have more limited legal rights (mainly housing-related, not general public access).
If you're considering either for a specific medical or emotional need, discuss the right fit with your doctor, who can also provide necessary documentation.