I still see a lot of confusion from people who mix up terms and don't really know what they are looking for when it comes to towing a vehicle the first time. I currently do not tow anything as I now have a smaller RV that gets me into most places I want to go. And I travel mostly in the west where the wide open spaces are greater. and easier to move around. That is a personal choice. If you have a larger RV, you most likely need to tow a vehicle to get around and do some real sightseeing or shopping.
A tow dolly is two wheels, an axel and a tongue. This allows you to tow almost any vehicle including front wheel drive models, without adding the miles to them. You don't need to think about the model as much or installing a base plate. With 4 wheel drives, rear wheel drives and all wheel drives, you may need to look at disconnecting and/or removing the drive shaft. The tow dolly also adds weight. They can be anywhere from 500 to 1500 pounds that you need to add into your overall towing weight. You may also need one with brakes. Check for state laws on whether you need a license for your tow dolly.
A tow bar or tow hitch is attached to the RV or towing vehicle and then to the vehicle being towed. This has now become pretty easy to do and can be done by one person. The bar can be mounted on either the RV or the vehicle. You need to get a base plate for your particular vehicle as well. The bars can be stowed when not in use compared to dollies which have to always be dealt with in some way.
It is best to have your tow vehicle or have one in mind when you buy the tow bar. Different models, weight and ground clearance all have to be considered together. You tow the vehicle with all wheels down with the tow bar.
With either option, check with your vehicles manufacture for any special considerations or for things you need to know. Some vehicles just make better toads than others.
Whatever method you choose, make sure to do the required maintenance for safe use. Remember that you can't tow and drive like normal all the time. You can't just throw it into reverse and back up when you are all hooked up with a tow vehicle. Both methods require the proper chains and light hookups.