What is the difference between part and manufacturer part?
A part is something that you (or your company) designs, controls and produces (although you may out-source the manufacturing of it). It is something that usually has it’s design controlled by either a document management system or part lifecycle management system.
A manufacturer part is usually a part that has it’s parameters specified and controlled by another company or organization, but which you use in making your part/assembly. this can be something specialized (CPU fan), or something very common (nuts and bolts).
The big difference is that with parts, you control how it is revised because the specifications are controlled by you (or your company). You do not control the specifications for manufacturer parts, you know them and make the decisions to use them in your designs.