A bill of material (BOM) in SAP lists the components, parts, and quantities needed to assemble a product. It contains the object number, quantity, and unit of measure for each component. There are different types of BOMs for materials, equipment, functional locations, document structures, orders, and work breakdown structures. BOM data is used in production planning for activities like MRP, work scheduling, and production order management. BOMs can be variant for similar products or multiple for different configurations of a single product. A BOM has a header, items specifying each component, and optional sub-items for partial component quantities installed in different locations.