-USE-MOUSE-ACTION is non-nil, invoke the button's mouse-action
-instead of its normal action; if the button has no mouse-action,
-the normal action is used instead. The action may be either a
-function to call or a marker to display and is invoked using
-`button-activate' (which see).
+USE-MOUSE-ACTION is non-nil, invoke the button's `mouse-action'
+property instead of its `action' property; if the button has no
+`mouse-action', the value of `action' is used instead.
+
+The action in both cases may be either a function to call or a
+marker to display and is invoked using `button-activate' (which
+see).