In Dubai the category has a specific regulatory meaning. A chauffeur service is a limousine operation licensed by the Roads and Transport Authority, using vehicles registered for that purpose and drivers holding the RTA professional driver permit. It is booked in advance at an agreed price. It is a separate licence class from the metered RTA taxi, and separate again from the ride-hailing apps.
The practical difference shows up at the airport and in the heat. A limousine booking has a named driver assigned before you land, a vehicle waiting in the designated pickup area rather than a queue, and a price that was fixed when you booked. Tolls, the airport access charge and the taxes are inside it. Between May and September, when standing outside for ten minutes is genuinely unpleasant, knowing exactly where the car is stops being a convenience and starts being the point.