What is a system of tracks used for the making up of trains and storing of cars?

A yard is specifically designed for the making up of trains and storing of cars. This area typically consists of multiple tracks where rail cars can be assembled into trains or disassembled after they have completed their route. It serves essential functions in rail operations, such as sorting freight or passenger cars, performing maintenance, and facilitating the transport of goods by allowing for the easy organization and access to rail cars.

The other options, such as depot, terminal, and station, refer to different functionalities within rail transport. A depot mainly serves as a location for storing and servicing rolling stock, while a terminal generally refers to a station at the end of a rail route where passengers can board and alight from trains. A station functions as a stopping point for passengers but does not provide the same extensive arrangement or storage capabilities as a yard. Therefore, the yard is the most accurate choice for the function described in the question.