The little flat green thing in the road, that's a Toad right??

In the RV community a Toad isn't little, probably not green, doesn't get squished flat (very often) and isn't even an animal.
A Toad is the nickname for the vehicle that gets dragged around behind the rig. 
The towed vehicle. Towed = Toad - get it? 
If you don't like Toad then Dinghy Vehicle or just "Dinghy" is another term, that one comes from the boat world where a sailboat will tow a small boat (named a Dinghy) behind it to use to go ashore when the big boat is anchored away from the beach.

That white car is tailgating us again!

You've probably seen an RV sailing along pulling a little car or a Jeep behind it. Looks easy but it takes a little planning.

First off you can't tow any vehicle, at least not with all 4 wheels on the ground (called Flat Towing or 4 Down). It takes a little research to find a vehicle that can be towed flat. Jeeps are good candidates as are Honda CRV's. Saturns used to be popular but they quit making them. 

We bought a Ford Fiesta. Whatever it is, it is essential to check that the manufacturer approves of it being towed and what conditions they might specify for towing. 

Our Fiesta has a routine that has to be followed or the transmission can be wrecked. First put on the parking brake, turn on the ignition, shift the transmission to neutral and wait for a "Transmission Ready" message on the information screen, turn off the ignition, then DISCONNECT THE NEGATIVE CABLE FROM THE BATTERY, Then you can tow it as far as you like but don't exceed 70mph.

Attention, Attention Will Rodgers. Having owned this Fiesta for 3 years now and having put only 35,000 miles on it I would NEVER EVER buy a Fiesta again. The transmissions are terrible and ours has had major repairs already. They are all the same and Ford have had to extend the warranty on the transmissions to 150,000 miles to try and calm the angry owners.

ANOTHER UPDATE.
We now have close to 60,000 miles on the Fiesta, it's had 4 major transmission repairs under the extended warranty from Ford. After the last ne they told us "NO MORE" they now claim all the rattling, lurching and hesitating is "NORMAL" for this transmission and we will have to live with it. Obviously nobody would buy a used car with a transmission in this condition so we are now in a "Mass Action Suit" (Not the same as a Class Action) against Ford. I personally do not recommend anyone buy a Ford vehicle with this or a similar computer controlled geared transmission. Ford Fiesta, Focus and Fusion vehicles are all cursed with this same problem.
BUYER BEWARE!!

Other vehicles have completely different set ups for towing and some can be towed if you have changes made to the drive train such as devices to uncouple the drive-shaft in rear wheel drive vehicles.

Some vehicles can only be towed on a trailer or a "Tow Dolly" which lifts the front wheels of the vehicle on to a 2 wheel trailer so the drive wheels don't go round while moving.

So then off you go towing? 

Nope. There is a Tow Bar between the RV and the Toad. That needs to be rigidly attached to the Toad, This requires that a subframe be installed that attaches to the toad chassis. 

The subframe is behind the radiator grille the two prongs sticking out are where the tow bar attaches and they can be removed when not in use

Some method of using the toads rear lights for brake lights, running lights and turn signals needs to be worked out. Some can be tied straight into the existing lights with diodes to isolate the power from the RV from the toad electrics. Ours has a new bulb holder installed in the rear lights that connects directly to the RV and has no connection at all to the toad.

Fiesta ready to roll

Tow Bar, safety cables and electrical cord set, and the "Y" shaped legs of the tow bar locked.

Off we go!

No. 
Because of the weight of the toad, some kind of braking system needs to be installed so that in an emergency when you jam on the RV brakes, the brakes in the toad also come on and help keep the whole ensemble stable. Various systems use inertia, the brake light switch, air or electric actuators to achieve the desired result.

Tow now? 

Sure just as soon as you attach the tow bars, safety cables/chains and electrical cord and set up the brake system in the toad, pump the brakes a couple of times to set them up, go thru the transmission tow routine, Check the lights are working, take the parking brake off and check the tow bar is locked.

If you're like me you'll be watching the toad in the rear view camera for the first 5 miles hoping it doesn't suddenly fall off.

And believe me all this stuff is NOT CHEAP.

Our rig with the toad behind it is 55 FEET LONG! The whole thing loaded and ready to go weighs 10 TONS. Please don't cut in front of a loaded rig, he's leaving the gap in front so he can stop if there's an emergency. Plan ahead and slow down behind him if you're nearing your exit. 
THANKS BnB