In few words it means:
{ and end with }. They can contain a list of unordered set properties through , (comma). or null.[ and ends with ]. It can contain a list of unordered set values through , (comma).Please, always set comma between objects and values, but not at the end of a list. The Sellector will not be displayed if you misplace the comma.
More about JSON at: http://www.google.co.uk/search?btnG=1&pws=0&q=json
