A transfer case is part of the drivetrain system in four-wheel and all-wheel drive vehicles. It connects the transmission to the front and rear axles and allows the driver to switch between different drive modes, such as two-wheel drive, four-wheel drive high, and four-wheel drive low. The transfer case also distributes the engine power to the front and rear wheels according to the selected mode. A transfer case can be mechanical or electronic, depending on the type of vehicle and its features.