The prefix key C-x 5 is analogous to C-x 4. Whereas each C-x 4 command pops up a buffer in a different window in the selected frame (see Pop Up Window), the C-x 5 commands use a different frame. If an existing visible or iconified (a.k.a. “minimized”, see Visibility of Frames in The Emacs Lisp Reference Manual) frame already displays the requested buffer, that frame is raised and deiconified (“un-minimized”); otherwise, a new frame is created on the current display terminal.
The various C-x 5 commands differ in how they find or create the buffer to select:
Create a new frame (
Select buffer bufname in another frame. This runs
Visit file filename and select its buffer in another frame. This
find-file-other-frame. See Visiting.
Select a Dired buffer for directory directory in another frame.
dired-other-frame. See Dired.
Start composing a mail message in another frame. This runs
compose-mail-other-frame. It is the other-frame variant of
C-x m. See Sending Mail.
Find the definition of an identifier in another frame. This runs
xref-find-definitions-other-frame, the multiple-frame variant
of M-.. See Xref.
Visit file filename read-only, and select its buffer in another
frame. This runs
You can control the appearance and behavior of the newly-created frames by specifying frame parameters. See Frame Parameters.