Here is an overview of the toolbar changes on edit screens in Joomla 1.6.

The Apply button has been renamed to Save.  This button will save the current page then return to it so you can continue to work on it.

The Save button has been renamed to Save & Close.  This button will save the current page then return you to the list managing that content.

The Save & New button is new.  This button will save the current page, then return you to a new blank item, avoiding going back to the list in between.

The Save as Copy button is also new.  This button will save the current page as a copy of the original, then return you to that copy so you can continue to work on it.  The original content is not changed in the process.

The Close button simply returns you to the list managing the content without saving.