Objects own a set of properties that are named containers for values. You can create new properties belonging to the object itself or to its prototype if you want to share them among all instances of an object class. Using the object and property reference as an LValue allows you to assign a new value to the property. To retrieve the property value, use it as you would any other RValue.

Cross-references:

ECMA 262 edition 2 - section - 8.6.1

ECMA 262 edition 3 - section - 8.6.1