Workspaces are the different layouts in the Blender application that are setup to more efficiently work in different aspects of the Rendering workflow.
They’re basically a setup of the tools available, with a name. I have used this in other tasks, but Blender does them real justice. In all of the work that you can do in Blender, the workspaces are properly setup to reflect a “stage” in which you’d work.
The Layout Workspace, for example, is where you’d do all your… layout (d’oh), which is ages before you get to the point of animating, shading or rendering. So, pay attention to that.