Inventory management is the practice of knowing what you have, where it is kept and how fast it moves. It covers receiving goods, storing them, picking them for orders and counting them periodically to check the records match the shelves.
A builders' merchant with several yards, for example, needs to know whether a delivery of timber can be fulfilled from the nearest site or must be transferred. Good systems set reorder points, flag slow-moving lines and keep stock figures consistent between tills, warehouse and accounts, which reduces both shortages and over-ordering.