SAP Notes are very well known since beginning of first SAP software. They are intended to help while supporting run of SAP applications. Basically the main purpose of the Notes is to fix an issue within the software. For details on the Notes and their types see here. Over the years another type of support document raised. It is SAP Knowledge Base Article (KBA).
The KBA are intended to complement the SAP Notes by depicting additional features or issues which are involved within particular SAP application. But the KBAs do not contain the code which fixes the issue. The code is solely provided by the Notes.
Both the Notes and KBAs are available via SMP at: