Begin editing on filename. If no filename is given, start over with a copy of the current file. Add a ! to edit the new file even if the current file has not been saved since the last change. With the +num argument, begin editing on line num. Or num may be a pattern, of the form /pattern.
:e fileEdit file in current editing buffer
:e +/^Index #Edit alternate file at pattern match
:e!Start over again on current file