Before you can save a new document you have to give it a name. The Save As... menu command is used to save a document under a certain name. The Save menu command is used to save a document that already has a name. If you are saving a new document for the first time you will need to use the Save As command and give it a name. If you try to use the Save command to save a document that doesn't have a name you will be greeted with the Save As dialog box.