When you go through the process of publishing services or creating service definitions using the Service Editor in ArcGIS Desktop, occasionally you'll need to come back to your service configuration at a later time. For example, if you attempted to publish a map service but noticed there were a substantial number of errors after analyzing your map document, you may need to close ArcMap and come back to correct those errors in a future session. If you encounter this scenario in your work, you can save your service or service definition configuration as a draft when you close the Service Editor.
You can think of a draft service or draft service definition as a work in progress. Although the draft may contain all the service properties you want to include for the service, a draft has not been compiled; that is, it does not contain any GIS resources and data that might be published to the server or staged locally on disk. Once you complete your draft and commit to publishing your service or saving your service definition, your GIS resources and data are compiled and the draft is deleted.
Drafts can only be opened in ArcGIS Desktop, since they rely on the GIS resource (map document, database, and so on) and the ArcGIS Server connection that was used to create them. This is important to keep in mind, since you'll need access to the GIS resource and server connection used to create the draft to complete your service configuration.
For full instructions on how to open draft services or draft service definitions, see Opening a draft service in ArcGIS Desktop.