BOM items differ according to their objects. There are BOM items with materials, documents and without objects (for example, text items). You can define an object category here for each type of BOM item that will show you the type of item in each case in the general item overview screen.
The assignments are for information purposes only.
You should plan to use only simple BOM structures with few object categories. For example, if you do not use document administration you can easily avoid great deviance in the object categores.
Object category BOM item object
----------------------------------------Define the object categories for each BOM item.