-If @var{position} is less than 1, @code{set-marker} moves @var{marker}
-to the beginning of the buffer. If @var{position} is greater than the
-size of the buffer, @code{set-marker} moves marker to the end of the
-buffer. If @var{position} is @code{nil} or a marker that points
-nowhere, then @var{marker} is set to point nowhere.
+@var{position} can be a marker, an integer or @code{nil}. If
+@var{position} is an integer, @code{set-marker} moves @var{marker} to
+point before the @var{position}th character in @var{buffer}. If
+@var{position} is @code{nil}, @var{marker} is made to point nowhere.
+Then it no longer slows down editing in any buffer. If @var{position}
+is less than 1, @var{marker} is moved to the beginning of @var{buffer}.
+If @var{position} is greater than the size of @var{buffer}, @var{marker}
+is moved to the end of @var{buffer}.