What is the purpose of this software

I reckon your question is smart and important and it highlights MS's serious failure to adequately explain to the world the purpose and value that SharePoint could provide. I have seen, even in a global corporation that could afford to do it right, what amounted to "SharePoint failure" - but was really ECM failure. I reckon there are many "SharePoint failures" out there. Sharepoint failure is when everyone just quietly avoids using it and drifts back to windows folders. I suggest reading this book "Enterprise Content Management with Microsoft SharePoint" By: Christopher Riley, Shadrach White, or some other similar book.

Document management but also a 'view' on what used to be 'just' shared folders. It also supports/is aligned with One Drive. I would say that it is becoming more a backbone/framework rather than a frontend like it was remembered... i still remember people talking about Sharepoint to build websites...

Enterprise document management solution for organizations

Business Colaboration between all Employees, like sharing files, custom apps, workflows, intranet sites, directory, Org Chart, project & task management and a lot of many useful features.

This is a document library, where you can share documents and keep track of changes. Also SharePoint is heavily used for creating sites (intranet ones) which is one of the greatest features. With O365 bundle, it’s always available, of course depending on Microsoft service availability, but still pretty consistent. You can manage libraries, lists and give permissions on granular level. Like access to site, yes, but to a list, maybe not.

I also love that you can access the cloud based server anywhere. I can look up documents are home or from another work computer easily.

SharePoint is an excellent document sharing repository system. You can keep multiple versions of the same document with a detailed document history and track changes etc. I love it!