Workspaces allow you to easily group targets based on your workflows (ex. different engagements, projects, clients, etc).
You can change the current workspace from the dropdown menu pinned in the top left corner of the page. All scans that you do will go to the current workspace.
You can see how many base targets you have defined for each workspace on the Workspaces page
You can add a new workspace by clicking the +Add workspace button, a pop-up will appear where you can fill in the details.