The multi-tenant mode allows you to create multiple workspaces.
The workspace term is just a label, you can rename it to anything you find appropriate to your business model. Examples are Organizations, Companies, Teams, etc.
After a new user signs up, they are asked to create a new workspace.
If the user has been invited but didn't come from the invitation email, they will be asked if they want to accept the invitation or create a new workspace.
Users can switch, create, edit or delete workspaces on the Workspaces page that can be accessed via the User's menu. Permission to edit and delete a specific workspace depends on the role the user has on that workspace.