Creates a new tab with a blank, untitled file. If you click the File|New item directly, then the file type for the new file is the one for which you selected "default file type for new files" in the file type configuration. If you select a file type from the File|New submenu, then the new file uses the settings for the file type that you selected.
If you use File|Save As and give the file a name with an extension that belongs to a file type other than the one used by File|New, then the file's file type is be changed to the file type associated with that extension. The file will then also use the settings defined for that file type.
Options|Configure File Types