The answer to that question is pretty much anything you want. However there are certain rules and regulations that you have to abide by. For the most part people select trainers so that they can move large objects. This can take the form of waste from a garden, heavy furniture in a house move, general large items that need to be transported from one location to another or even, if it is a converted unit, horses.
When you have the trailer attached to your car you should begin to think about what weight it can actually handle. It is impossible for many cars to tow large objects. Most trailers are specifically designed to accommodate SUV or Estate vehicles. Smaller objects can be towed in cars with a lower horsepower.
The trailer will have specific dimensions that you can choose before you set out. Bear in mind what items and what volume of material you are going to need to move before you order one. Should you need them, Trailer Parts are available from https://autoandtrailer.com/shop/trailer-parts.
Once you have the trailer that is correct for you then the sky is really the limit. You should also think about the fact that you will have to drive this vehicle on the road where other users will be present. Having a trailer at the rear of the car means you have to be even more considerate than you would normally be. However, with care and skill you should be able to use the trailer to its full capacity and function.