By default a workspace will not store the file revisions in the workspace (light workspace). The workspace creation is very quick because it only has to get the file head revision data. The workspace database is small because it does not store any file revisions. When you checkout a file the head revision is stored in the workspace database so you can view your changes without connecting to the server.
The big disadvantage with light workspaces is when you are working offline. You will not be able to open previous revisions in the Show History Dialog and you will not be able to view any submitted changesets.
If you work away from the server a lot of the time we therefore recommend you enable this option to create a full workspace.