Workspace, in my opinion, something that everyone forgot to mention, it’s a way to create an area with all tools you need to address a single language, like other said, in one project you might have PHP, Phyton, JavaScript, Node, etc.
Creating a Workspace for each specific language you can have all tools for managing, debugging, testing, for example all your JavaScript.
This is much easier to manage, so you can have a workspace for PHP, another for Node, ... and one project that have folders in multiple workspaces.
Hope I have helped!