After you've created a workspace, you can start developing features in it. You can both create new features from scratch and add existing features from production to the workspace. You can also remove features from the workspace. When you're done developing and testing the features, you can move them to production by publishing the workspace.
Features created in a workspace are no different from ones created outside the workspace, except that, until published, they are only available in the workspace and therefore have no impact on the live content of the site.
For more information about developing features in workspaces, see: