A property list (plist for short) is a list of paired elements. Each of the pairs associates a property name (usually a symbol) with a property or value. Here is an example of a property list:
(pine cones numbers (1 2 3) color "blue")
This property list associates pine with cones,
numbers with (1 2 3), and color with
"blue". The property names and values can be any Lisp objects,
but the names are usually symbols (as they are in this example).
Property lists are used in several contexts. For instance, the
function put-text-property takes an argument which is a
property list, specifying text properties and associated values which
are to be applied to text in a string or buffer. See Text Properties.
Another prominent use of property lists is for storing symbol properties. Every symbol possesses a list of properties, used to record miscellaneous information about the symbol; these properties are stored in the form of a property list. See Symbol Properties.
This predicate function returns non-nil if object is a
valid property list.