A bill of materials (BOM) is a tabular listing of the components of a SOLIDWORKS PDM item or a SOLIDWORKS assembly, drawing, or weldment part.
Item Explorer displays item BOMs and item named BOMs in the Bill of Materials tab. To view other BOM types, use File Explorer.
When you generate items, it is possible to attach multiple configurations of a part to the same item. This can cause the BOM structure in Item Explorer to display differently from the BOM structure in File Explorer. To make the BOM structure in Item Explorer mirror the BOM structure in File Explorer, when you generate items, give each configuration of the part a separate item ID.