A loft bunk bed is technically defined as a bunk bed in which the top of the mattress is more than three feet from the floor. As such, virtually all bunk beds are actually loft bunk beds under this definition.
In use, however, loft bunk beds often have simply one twin bed on top with nothing underneath. In addition, they are typically more self-contained in that they include many other features and/or furniture items that typically reside in a bedroom. For instance, loft bunk beds can include both a desk and drawers underneath the twin bed on top.
Loft beds are a viable alternative to traditional beds and other bunk beds. These beds can be purchased both online and offline and many options are available with regards to styles and colors. The beds are typically available in both wood and metal construction.