Most components carry a manufacturer part number (MPN), but many companies also refer to parts by their own internal numbers — to match an existing scheme, a legacy system, or paperwork that predates PartsBox. PartsBox lets you keep both.
PartsBox has two kinds of part with an MPN-related identity. A linked part has an online identity, normally its MPN, and by default that MPN is its name. On a commercial plan you can rename a linked part or give it an internal part number; PartsBox then stores both the MPN and your number, shows both in tables, and finds the part by either one when you search. A local part has no online identity and is referred to by whatever name you give it — generic or no-name components, PCBs, mechanical parts, anything without an exact MPN.
Keeping both numbers means you can name a part the way your company already does, without losing the manufacturer's number that pricing, purchasing, and BOM matching depend on. Distributor offers, datasheets, and specifications keep following the MPN; your number is what people see and type.
You can assign the internal number the moment you create a linked part, so the part never exists under a name your team does not use. Search finds the part by either number — it does not matter which one you remember. Your number appears wherever the part's name does: in tables, on printed labels, on pick lists, and in exports.
A BOM that refers to parts by your internal numbers still imports cleanly. BOM import matches each line against part names as well as MPNs, so a CSV from your CAD tool can carry your numbering and match the right parts. The same goes the other way: paperwork you produce from PartsBox shows the numbers the rest of your company expects.
On the free Maker plan, linked parts keep their MPN as the name and cannot be renamed. Internal part numbers start on the Essentials plan.