A tiny house (or small house) is essentially a custom built building sitting on a towable trailer of some kind. They can be similar to a travel trailer, or a fifth wheel trailer, but resemble a regular home and not an RV.
They are usually constructed with more traditional building materials, much like a regular home, but on a smaller scale.
The biggest advantage of a tiny house is cost. Some tiny house owners even build their own, and in some cases most of the materials are reclaimed or recycled, thus lowering the cost to the bare minimum.
Another advantage of a tiny house is that, because they are built from scratch, there is no limit to the amenities you can put in them. For example, there are very few RV manufacturers that put full sized bathtubs into an RV, but in a tiny house you can.
Many tiny houses come with residential appliances. Plus there can be many space saving techniques such as using murphy beds, or other ways of multiplying the use of the space. (for example, a table that folds into a desk, or folds up against the wall when not in use).
A disadvantage of a tiny house is that some are not built with holding tanks for water and sewer like an RV. Therefore you MUST be hooked up to either residential service, or park in an RV park that has full services.
Another disadvantage may be that you need to purchase large pickup truck to pull a tiny house, depending on its size.
Yet another disadvantage is that some RV parks will not accept a tiny house.