In 2011, the European Committee for Standardization (CEN) published EN13809:2003, providing a definition of the term “tourist guide” (“tour guide” in US English):
Tourist Guide is a Person who guides visitors in the language of their choice and interprets the cultural and natural heritage of an area, which person normally possesses an area-specific qualification usually issued and/or recognised by the appropriate authority.
Therefore, only qualified and licensed guides are allowed to interpret the cultural and natural heritage of an area. In Greece there is no such a thing as a “driver guide“, as this implies offering two distinct services simultaneously, something prohibited by the law.
Please bear in mind that all licensed guides should have a badge that looks like the one you see below. When you contact people on the internet that present themselves as “guides”, don’t hesitate to ask their credentials.