Load variances
Various cars and caravans can obviously carry different loads which is why their tyres are designed specifically for whatever that limit may be. Passenger rated car tyres are made of a lighter construction which means they can handle higher speeds with lighter loads, the opposite applies to truck tyres, which are typically found on caravans, and have better resistance offroad with a higher load-carrying capacity, and lower speed rating.
The standard tyres which are found on most cars are P-rated radial tyres made of parallel fabric casing cords, making them more flexible so that the tread stays in contact with the road when taking corners. These tyres have several layers of steel fabric around the inner circumference under the tread. This prevents too much tread movement when slowing down, starting and stopping.
4WDs and utes
Most of you are likely towing your caravan with a 4WD or ute which will have a similar load rating to what you are towing. This is why the majority of 4WDs feature LT tyres, created for commercial load-carrying. This is one scenario in which wheels and tyres should be matched across the rig so the spare wheels can be used. There are a variety of stud patterns available to match your caravan and vehicle wheels.
If you are considering this, ensure the pitch circle diameter is correct. Your wheels fit tight with identical offsets, a measurement usually stamped on the inner rim.