+@vindex delete-active-region
+ As described in @ref{Erasing}, the @key{DEL}
+(@code{backward-delete-char}) and @key{delete}
+(@code{delete-forward-char}) commands also act this way. If the mark
+is active, they delete the text in the region. (As an exception, if
+you supply a numeric argument @var{n}, where @var{n} is not one, these
+commands delete @var{n} characters regardless of whether the mark is
+active). If you change the variable @code{delete-active-region} to
+@code{nil}, then these commands don't act differently when the mark is
+active. If you change the value to @code{kill}, these commands
+@dfn{kill} the region instead of deleting it (@pxref{Killing}).
+
+@vindex mark-even-if-inactive
+ Other commands always operate on the region, and have no default
+behavior. Such commands usually have the word @code{region} in their
+names, like @kbd{C-w} (@code{kill-region}) and @code{C-x C-u}
+(@code{upcase-region}). If the mark is inactive, they operate on the
+``inactive region''---that is, on the text between point and the
+position at which the mark was last set (@pxref{Mark Ring}). To
+disable this behavior, change the variable
+@code{mark-even-if-inactive} to @code{nil}. Then these commands will
+instead signal an error if the mark is inactive.
+