What is the Different between JSON and YAML?

JSON  =  Java script object notation. 

What It Is:

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language,Standard ECMA-262 3rd Edition - December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.

More details here: 
https://www.json.org/

YAML = YAML Ain't Markup Language

What It Is:

 YAML is a human friendly data serialization  standard for all programming languages.

More Details here:

http://yaml.org/

Sample JSON:

{
  "QueryResponse": {
    "maxResults": 1,
    "startPosition": "1",
    "Employee": {
      "Organization": false,
      "Title": "Mrs.",
      "GivenName": "Jane",
      "MiddleName": "Lane",
      "FamilyName": "Doe",
      "DisplayName": "Jane Lane Doe",
      "PrintOnCheckName": "Jane Lane Doe",
      "Active": true,
      "PrimaryPhone": { "FreeFormNumber": "505.555.9999" },
      "PrimaryEmailAddr": { "Address": "janedoe@example.com" },
      "EmployeeType": "Regular",
      "status": "Synchronized",
      "Id": "ABC123",
      "SyncToken": 1,
      "MetaData": {
        "CreateTime": "2015-04-26T19:45:03Z",
        "LastUpdatedTime": "2015-04-27T21:48:23Z"
      },
      "PrimaryAddr": {
        "Line1": "123 Any Street",
        "City": "Any City",
        "CountrySubDivisionCode": "WA",
        "PostalCode": "01234"
      }
    }
  },
  "time": "2015-04-27T22:12:32.012Z"
}

Sample YAML

---
QueryResponse:
  maxResults: 1
  startPosition: '1'
  Employee:
    Organization: false
    Title: Mrs.
    GivenName: Jane
    MiddleName: Lane
    FamilyName: Doe
    DisplayName: Jane Lane Doe
    PrintOnCheckName: Jane Lane Doe
    Active: true
    PrimaryPhone:
      FreeFormNumber: 505.555.9999
    PrimaryEmailAddr:
      Address: janedoe@example.com
    EmployeeType: Regular
    status: Synchronized
    Id: ABC123
    SyncToken: 1
    MetaData:
      CreateTime: '2015-04-26T19:45:03Z'
      LastUpdatedTime: '2015-04-27T21:48:23Z'
    PrimaryAddr:
      Line1: 123 Any Street
      City: Any City
      CountrySubDivisionCode: WA
      PostalCode: '01234'
time: '2015-04-27T22:12:32.012Z'

Relation to JSON

Both JSON and YAML aim to be human readable data interchange formats. However, JSON and YAML have different priorities. JSON’s foremost design goal is simplicity and universality. Thus, JSON is trivial to generate and parse, at the cost of reduced human readability. It also uses a lowest common denominator information model, ensuring any JSON data can be easily processed by every modern programming environment.

In contrast, YAML’s foremost design goals are human readability and support for serializing arbitrary native data structures. Thus, YAML allows for extremely readable files, but is more complex to generate and parse. In addition, YAML ventures beyond the lowest common denominator data types, requiring more complex processing when crossing between different programming environments.

YAML can therefore be viewed as a natural superset of JSON, offering improved human readability and a more complete information model. This is also the case in practice; every JSON file is also a valid YAML file. This makes it easy to migrate from JSON to YAML if/when the additional features are required.

JSON's RFC4627 requires that mappings keys merely “SHOULD” be unique, while YAML insists they “MUST” be. Technically, YAML therefore complies with the JSON spec, choosing to treat duplicates as an error. In practice, since JSON is silent on the semantics of such duplicates, the only portable JSON files are those with unique keys, which are therefore valid YAML files.

It may be useful to define a intermediate format between YAML and JSON. Such a format would be trivial to parse (but not very human readable), like JSON. At the same time, it would allow for serializing arbitrary native data structures, like YAML. Such a format might also serve as YAML’s "canonical format". Defining such a “YSON” format (YSON is a Serialized Object Notation) can be done either by enhancing the JSON specification or by restricting the YAML specification. Such a definition is beyond the scope of this specification