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 (“minimized”) frame already displays the requested material, these commands use the existing frame, after raising or deiconifying (“un-minimizing”) as necessary.
The various C-x 5 commands differ in how they find or create the buffer to select:
make-frame-command).
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.
Here is an example of using default-frame-alist to specify
the default foreground color and font:
(add-to-list 'default-frame-alist '(font . "10x20"))
(add-to-list 'default-frame-alist '(foreground-color . "blue"))
By putting such customizations in your init file, you can control the appearance of all the frames Emacs creates, including the initial one (see Init File). See Fonts, for other ways to set the default font.