SharePoint is Microsoft's collaboration platform, similar to Google Drive, yet much more. It's a place where team members can communicate, exchange data, and work together; a shared file repository, blog, web content management system, and an intranet.
Some years ago, cutting-edge Microsoft collaboration had two components: Exchange, which powered email and shared calendars, and network file drives. These drives, which you might remember had drive letters such as "S" and "X," housed files your whole team could access, but only one person could edit them at a time. As a workaround, you could copy them to your local machine and edit there. This would sometimes lead to confusion, lots of overwriting, and cryptic file names.
Microsoft created SharePoint, which provided a few advantages:
In a clever move, Microsoft also retained the old file drive concept, meaning you could open an Excel file from your "X" drive, modify it, then save it, just as before. However, in the background, SharePoint would check the file out for you, then check it back in and version it for you. These features still exist and work well, but SharePoint is more than just a fancy file drive today.
As Google, Apple, DropBox, and others improved the capabilities of their cloud services, Microsoft was working on their own. A new file-sharing service called SkyDrive (now OneDrive) took over simple file sharing. With that, SharePoint became an important component of Microsoft's 365 product, which paired cloud-based collaboration with subscription-based access to Office.
SharePoint is a web content platform, but not precisely the WordPress or Squarespace you probably associate with this term. You could use SharePoint to create pages and publish them as a website, but you could also create a site for a department team, then drop Web Parts into it that might include a blog with announcements, a list of team members from Exchange, a library of documents, and a grid of data-driven by an Excel workbook.
As a public-facing web CMS, it was adequate, but as an intranet that could show bits of corporate data, it was pretty cool.
Today's SharePoint builds on its strengths and is compatible with Windows, macOS, Android, iOS, and web browsers. It retains the same concept of a site, but recent versions introduced the ability to add apps to that site. Third-party developers even have a marketplace in which they can offer their own.
SharePoint is like a home base for your team where you can collect files, discussions, announcements, and just about any other form of collaboration you can imagine.
SharePoint is available as part of Microsoft 365, but only for business accounts. That said, these accounts can be had for as little as $5/month.
The central concept in SharePoint is a Site. You need to set up a Site first, then you can add content or widgets to it.
While SharePoint used to be a CMS much like WordPress, where you input content and it was published to a public website, the Microsoft 365 version is more commonly used as a collaboration space.