Features of an Item Category 
When you create a new BOM item, you must select an item category for the item. The item category defines the features and functions of an item. The item category determines which specific item data is processed and controls further activities in the system.
If you define an item category for materials with a material type that is kept in stock, stock can be checked automatically.
In Customizing for Production, you define the features of the item category by choosing Bill of Material → Item Data → Define item categories. To define an item category, you answer the following questions:
- Is a material number a required entry?
- Is the item to be checked against stock?
- Is the item a text-only item with no further functions?
- Are different-sized sections of the item to be entered?
- Are negative quantities allowed?
- Are sub-items supported?
- Is the item a plant maintenance (PM) structure element?
- Is the item an intra material?
- Is the item a document item or class item?
- Which screens are selected and which fields appear on the item detail screens?