JSON is a data format based on a subset of JavaScript.
A simplified version of the specification is available on the JSON page. Full specification available as RFC IETF.
Libraries exist in different languages for converting from a JSON data string to data structures suitable for that language (and for switching to the other side). A list of some of them can be found at the bottom of the JSON homepage.
An array is a data structure common to most programming languages that contains a number of variables in a specific order. JSON has an array data type.
A JSON object is a serialization of a collection of key / value pairs. Most programming languages have an appropriate data structure, such as a hash in Perl or a (simple) object in JavaScript.
The page you are linking to does not mention JSON. It has a variable ( weatherData ), which is assigned a simple object (using the object literal {} ), which has one key ( reports ), which is assigned an array (using the array literal [] ), which contains several objects, each of which consists of groups of key / value pairs, where the values are all strings.
If you were to remove the first line and the half-line at the end, then an example would be a JSON data structure representing the same information. This is due to the fact that, as I said earlier, JSON is based on a subset of JavaScript and that part of the example corresponds to a subset.