What is SharePoint?

When looking up what SharePoint is, you get a lot of different answers from the Internet:
1. Microsoft SharePoint is a browser-based collaboration and document management platform from Microsoft – Wikipedia.
2. Microsoft's content management system. It allows groups to set up a centralized, password protected space for document sharing. Documents can be stored, downloaded and edited, then uploaded for continued sharing. – SAIT Polytechnic Teaching – Glossary .
3. SharePoint is a web-based intranet that can help improve your organisation’s effectiveness by streamlining the management of and access to data. – Creative Sharepoint .
4. SharePoint is an enterprise information portal, from Microsoft, that can be configured to run Intranet, Extranet and Internet sites. – SharePoint HQ .
5. {..} SharePoint is a sort of sharing/blogging/wiki-style server that mainly provides a back end to Microsoft Office – Jack Schofield, Technical Writer Guardian newspaper, UK.