Engineering research and development, also known as R&D, is the systematic process of learning about and building new technologies for the purpose of designing a product. As opposed to scientific research, engineering research is not concerned with discovering how the world works, but rather how things can be made to function for a given purpose. Such research might involve much scientific study, however, as engineers work to create design solutions to real-world problems. The development part of engineering research and development refers to the attempt to actually build the final product; many stages of development, each with various degrees of readiness, may be required for the design to succeed.
The first step in creating a solution to a given problem in engineering research and development is to learn about the problem itself and how the solution must function. If no similar products exist, this step may require a lot of research in the physical sciences, such as physics or biology. For example, the new field of nanoengineering had no nanoscale products on which to base its designs; engineers needed to look to physics to get an idea of how potential products might work.
On the other hand, if there are existing products in the world closely-related to the one being designed, engineers will probably focus on studying the existing technology itself rather than the underlying science. In the case of designing an engine for an upcoming car model, engineers would probably benefit more from studying previous car engines themselves rather than theoretical thermodynamics, for example. Internal combustion engines have been in widespread use for more than a century, and a variety of configurations have already been designed, used, and evaluated for their strengths and weaknesses—there's no sense in recreating what has already been designed.
Development of a product in engineering research and development is usually an iterative process. In other words, it is impossible to know exactly how well a product will function even when a detailed design plan is drawn up. Even well-designed products are not perfect and have their weak points. Therefore it is very helpful to develop prototypes, or working models, to test ideas. These models are not intended to be sold to a customer or be mass produced as a final product. Rather, they are intended to give engineers a better idea of which components of the model need improvement and which seem to work well.
After a series of systematic testing of a prototype, engineers attempt to redesign a product based on the information gathered during testing. They might adjust their calculations and slightly tweak some of the weaker components of their design. There is no rule to how many prototypes must be developed before a final product is ready; the number depends on factors such as how novel the technology is and whether the product might pose a safety or environmental risk when used.