the short answer
A personal trainer focuses on the workout itself - cueing technique, spotting, and pushing you through live, in-person sessions priced by the hour. A fitness coach takes a wider view, guiding training, nutrition, habits, and accountability over months through programs and regular check-ins, often delivered online. The trainer owns the session; the coach owns the outcome.
Titles overlap and "coach" is not a regulated word everywhere, so the lines blur - especially online. Use this comparison to match the right role to the goal, not to argue over labels.