The prefix key C-x 5 is analogous to C-x 4, with parallel subcommands. The difference is that C-x 5 commands create a new frame rather than just a new window in the selected frame (See Pop Up Window). If an existing visible or iconified frame already displays the requested material, these commands use the existing frame, after raising or deiconifying as necessary.
The various C-x 5 commands differ in how they find or create the buffer to select:
make-frame ). switch-to-buffer-other-frame . find-file-other-frame . See Visiting. dired-other-frame . See Dired. mail-other-frame . It is the other-frame variant of C-x m. See Sending Mail. find-tag-other-frame , the multiple-frame variant of M-.. See Tags. find-file-read-only-other-frame . See Visiting.
You can control the appearance of new frames you create by setting the frame parameters in default-frame-alist . You can use the variable initial-frame-alist to specify parameters that affect only the initial frame. See Initial Parameters, for more information.