Do you usually need to keep multiple copies of your sources, for instance, different versions, copies to test, your mates’ code, or what have you? You’ll need to use workspaces. A workspace is self-explanatory; it’s a space that contains your work. A workspace is yours; it’s a client-side copy of the items stored on the source control server. Your changes to your source-controlled items within the workspace are isolated until you check them in.
You can have multiple team projects in a single workspace and you can also have multiple workspaces for a source control server. To manage workspaces go to File > Source Control > Workspaces.
For more info, please visit: http://msdn2.microsoft.com/en-us/library/ms181383(VS.90).aspx