The Original Sharepoint
I was involved with some Sharepoint stuff very early in its evolution - about 2001 I think. And what not many people know is that Microsoft at that time had two completely different products, both badged as Sharepoint. From memory (it's over 20 years ago so don't @ me for not getting the details exactly right), one was built around a database, and the other was built around NTFS with extra metadata. They had completely different models and APIs, but they were both "Sharepoint".