Hints on Terminology 
Order BOM
The terms Order BOM and sales order BOM are interchangeable.
An order BOM is often created by engineering/design, for instance, if you have to redesign an assembly to fulfill customer requirements.
Note
You should not confuse creating an order BOM with changing the component overview in a production order, where it is not the product’s bill of material but rather it’s components that you change, without altering the material BOM.
The component overview in a production order is often changed by work schedulers, if, for example, a component, which is not available due to a bottleneck, has to be replaced. In this case you do not create an order BOM.
Finished Product, Semi-Finished Product, Raw Material
In this documentation we describe a material that:
was entered as a finished product in a sales order item
is, as a semi-finished product, simultaneously a BOM item and header for an assembly
is, as a raw material, a BOM item but not a header for an assembly
As a rule these descriptions correspond to the material types in the material master record. However, there is not necessarily any relationship between the material type and the use in a multi-level BOM. The material type can differ from the use in a multi-level BOM.