The Bill of Materials (BOM) is a list of things. In manufacturing, it is the recipe ingredients for producing (and repairing) equipment and machinery. It lists the raw material, parts, sub-assemblies, purchased items, and everything else that goes into the product.
The BOM acts as a key communication piece between departments. It contains items designed by engineering. A BOM provides the list of items to be purchased and the items that must be manufactured. It contains the identifiers (part numbers, stock numbers), the descriptions, quantities, purchasing details, manufacturer information, costs, and other key attributes.