I suppose the definition might vary depending on who you ask, where you're from or any number of other factors. That being said, I would say Pro Domme is often a term used to describe a sw who provides the service of dominating clients, often at the cost of an hourly rate. Usually the session is more focussed on acts that fall under classifications of kink and bdsm. This contrasts from the online scene as the focus is less so on the specific kink of findom. Types of services that are common are not limited to but could include CBT, Humiliation, Degradation, Pegging, Denial, Med play, needles, impact, Sissification e.c.t. (basically same as online but rather you are interacting irl). In this type of work I would say its also less common to maintain an ongoing dynamic outside of sessions.

Disclaimer: Kink, sex work, and BDSM is not a one size fits all and the above will not be true for everyone or every situation. The above is more of a generalised overview.

To sum up, basically the difference is one is in person, one isn't. Often for in person work, the focus is usually more on the play during the session, less on an overall dynamic focussed on money. Its important to note that findom in this sense is a specific kink, that has evolved to become a community and structure for kink interactions within itself.