The "B-B wheel arrangement" refers to a specific configuration of wheels on a locomotive or rail vehicle. In this arrangement, there are two sets of driving wheels, each set having two wheels. This design is commonly used in diesel and electric locomotives, providing good traction and stability while allowing for a compact design. The B-B arrangement is part of a classification system for locomotives, where letters represent the type of wheels and their arrangement. For example, the letter "B" indicates a pair of driving wheels. This system helps in understanding the capabilities and design of various locomotives in the railway industry.