Mark Commands
The following commands are used to mark positions in the buffer.
m ch
Store current point in the register ch. ch must be a lower-case ASCII letter.
m <
Set mark at the beginning of current buffer.
m >
Set mark at the end of current buffer.
m .
Set mark at point.
m ,
Jump to mark (and pop mark off the mark ring).
Emacs uses the mark ring to store marked positions. The commands m <, m > and m . not only set mark but also add it as the latest element of the mark ring (replacing the oldest one). By repeating the command m , you can visit older and older marked positions. You will eventually be in a loop as the mark ring is a ring.