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Lightweight data-interchange format, readable by humans and machines. Used to exchange objects from within programs across the open internet without tying them to language-specific implementations (i.e. converting objects from Ruby to PHP to Objective-C to….) by converting objects into arrays, dictionaries, and primitives.

Built on two structures:

• Dictionaries- key/object pairs. Fetched using NSDictionary's objectForKey:
• Arrays- objects stored at indexes. Fetched using NSArray's objectAtIndex:

The entire JSON is a dictionary.

Dictionaries are represented with curly braces. Arrays are represented with square brackets.

A colon pairs a key and an object.

See here for an excellent example.