underline and strike-through, background stipple, etc. Emacs provides
features to associate specific faces with portions of buffer text, in
order to display that text as specified by the face attributes.
+@xref{Faces}.
@item File Locking
Emacs uses file locking to notice when two different users
@xref{Undo}.
@item User Option
-A user option is a variable (q.v.@:) that exists so that you can customize
-Emacs by setting it to a new value. @xref{Variables}.
+A user option is a face (q.v.@:) or a variable (q.v.@:) that exists so
+that you can customize Emacs by setting it to a new value.
+@xref{Easy Customization}.
@item Variable
A variable is an object in Lisp that can store an arbitrary value.