-.Aq keys
-is in the form of zero or more modifier keys
-(MOD, Mod1, Shift, etc.) and one or more normal keys
-(b, space, etc.), separated by "+".
+.Ar combo
+is in the form of zero or more modifier keys and/or special arguments
+(Mod1, Shift, MOD, etc.) and a normal key (b, Space, etc.)
+or a button (Button1 .. Button255), separated by
+.Ql + .
+Multiple key/button combinations may be bound to the same action.
+.Pp
+Special arguments:
+.Bl -tag -width "anymodxxxx" -offset indent -compact
+.It Cm MOD
+Substituted for the currently defined
+.Ic modkey .
+.It Cm ANYMOD
+Select all modifier combinations not handled by another binding.
+.It Cm REPLAY
+Reprocess binding press/release events for other programs to handle. Unavailable for
+.Ic move ,
+.Ic resize
+and
+.Ic resize_centered .
+.El