Here we explain what is a shuttle transfer between a Paris address and a Parisian Airport
You can book a package holiday and book also for a "shuttle transfer", but maybe you not know exactly what it means.
Usually when get a package holiday with a shuttle transfer there is a minibus when you arrive and drops you and other people off in your Hotel destination in Paris.
It is most likely to be a private transfer either shuttles between your airport arrival and the the hotel or apartment address or between a train station and the airport. Such services are often independent of the hotel or package holiday, and you will be booked a voucher and allocated a seat on arrival at the minivan.
The Van is sometimes small and sometimes larger coach that literal words "shuttles back and forward" from hotels in Paris and Parisian ( CDG , Orly and sometimes Beauvais) . Occasionally it can be a private limousine or a people carrier type vehicle.
Very often you find them between different terminals of Charles deGaulle or Orly Airport - sometimes from the terminal to the car park or car hire place, sometimes from airport to hotels and back etc etc etc
Probably you are used to : most likely it will be a minibus that goes back and forth between the Airports and the hotels « shuttles back and forth » .