12.7 The Global Mark Ring
In addition to the ordinary mark ring that belongs to each buffer,
Emacs has a single global mark ring. It records a sequence of
buffers in which you have recently set the mark, so you can go back
to those buffers.
Setting the mark always makes an entry on the current buffer's mark
ring. If you have switched buffers since the previous mark setting, the
new mark position makes an entry on the global mark ring also. The
result is that the global mark ring records a sequence of buffers that
you have been in, and, for each buffer, a place where you set the mark.
The command C-x C-<SPC> (
pop-global-mark) jumps to
the buffer and position of the latest entry in the global ring. It also
rotates the ring, so that successive uses of C-x C-<SPC> take
you to earlier and earlier buffers.