JavaScript Object Notation (JSON) is a text format for the serialization of structured data.

It is derived from the object literals of JavaScript.

JSON can represent four primitive types (strings, numbers, booleans, and null) and two structured types (objects and arrays)

Primitive JSON

Here are four small JSON texts containing only values:
"Hello world!"
42
true
null

Object JSON

An object structure is represented as a pair of curly brackets surrounding zero or more name/value pairs (or members).

An object is an unordered collection of zero or more name/value pairs

A name is a string

A value is a string, number, boolean, null, object, or array.

Declare properties using name:value pairings separated by commas

Enclose names in curly braces

There is no trailing comma

This is a JSON object:

{
    "Image": {
        "Width":  800,
        "Height": 600,
        "Title":  "View from 15th Floor",
        "Thumbnail": {
            "Url":    "http://www.example.com/image/481989943",
            "Height": 125,
            "Width":  100
        },
        "Animated" : false,
        "IDs": [116, 943, 234, 38793]
    }
}

Array JSON

An array structure is represented as square brackets surrounding zero or more values (or elements).

Elements are separated by commas.

A value must be an

• object
• array
• number
• string
• three literal names
  1. true
  2. false
  3. null

This is a JSON array containing two objects:

    [
        {
           "precision": "zip",
           "Latitude":  37.7668,
           "Longitude": -122.3959,
           "Address":   "",
           "City":      "SAN FRANCISCO",
           "State":     "CA",
           "Zip":       "94107",
           "Country":   "US"
        },
        {
           "precision": "zip",
           "Latitude":  37.371991,
           "Longitude": -122.026020,
           "Address":   "",
           "City":      "SUNNYVALE",
           "State":     "CA",
           "Zip":       "94085",
           "Country":   "US"
        }
    ]

Number

The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. A fraction part is a decimal point followed by one or more digits.

String

The representation of strings is similar to conventions used in the C family of programming languages. A string begins and ends with quotation marks.

source: The Internet Engineering Task Force (IETF)