save-excursion

save-excursion is a special form in `C source code'.

(save-excursion &rest BODY)

Save point, mark, and current buffer; execute BODY; restore those things.
Executes BODY just like `progn'.
The values of point, mark and the current buffer are restored
even in case of abnormal exit (throw or error).
The state of activation of the mark is also restored.

This construct does not save `deactivate-mark', and therefore
functions that change the buffer will still cause deactivation
of the mark at the end of the command. To prevent that, bind
`deactivate-mark' with `let'.

If you only want to save the current buffer but not point nor mark,
then just use `save-current-buffer', or even `with-current-buffer'.