RTA stands for Ready-To-Assemble.
One of the main problems when shipping furniture is the relative low cost of the products vs the high cost of the shipping, due to the volume of the products. At some point in time, somebody invented RTA furniture (also called Self-assembly furniture). All the pieces of the product are shipped in a very compact box, with detailed instructions on how to assemble the unit, and is to be assembled at home by the buyer. Costs are saved by the assembly not being performed in the factory and by greatly reduced volumes for shipping and storage by the distributor and retailer. It comes in flat-packs, with instructions. Self-assembly furniture is very common in Britain, Europe, and Canada.
Many DIY (Do it yourself) oriented people actually like to assemble RTA units. The ease of assembly required varies. IKEA furniture, for example, is marketed on its completeness, including Allen keys in the package if needed. However, the assembly of some brands require the customer to have access to a much larger slection of hand or even power tools.
The most common types of self-assembly furniture are living room and office furniture, particularly bookcases and tables.
Self-assembly kitchens are available from some retailers. These are made to uniform sizes. They benefit from a wide number of options and the ability to easily update them through the addition of, for example, new cupboard doors.
Main brands in the U.S.: