explained properties in README.md

README.md

@@ -334,6 +334,30 @@ yl_speak_up.player_vars_save_file  JSON file containing information about
                                quest progress and quest data for individual
                                players.
 
+Properties
+==========
+NPC may have properties. A property is a value a particular NPC has. It
+does not depend on any player and will remain the same until you change
+it for this NPC. You can view and change properties via the "Edit" button
+and then clicking on "Edit properties". There are preconditions for
+checking properties and effects for changing them.
+
+Properties prefixed by the text "self." originate from the NPC itself,
+i.e. self.order (as used by many mobs_redo NPC for either following their
+owner, standing around or wandering randomly). They usually cannot be
+changed - unless you write a function for them. See
+	yl_speak_up.custom_property_handler
+and
+	custom_functions_you_can_override.lua
+You can also react to or limit normal property changes this way.
+
+Example for a property: mood of the NPC (raises when treated well, gets
+lowered when treated badly).
+
+Properties are also extremyl important for generic behaviour. Depending
+on the properties of the NPC, a particular generic behaviour might fit
+or not fit to the NPC.
+
 Generic behaviour
 =================
 Sometimes you may have a group of NPC that ought to show a common behaviour
@@ -362,7 +386,7 @@ The creator of a generic dialog can't know all situations where NPC may want
 to use his dialogs and where those NPC will be standing and by whom they
 are owned. Therefore only a limited amount of types of preconditions are
 allowed for the preconditions of this first automatic option: state,
-player_inv and custom.
+property, player_inv and custom.
 
 The other dialogs that follow after this first automatic dialog may contain
 a few more types of preconditions: player_offered_item, function and other