The standard JSON Format for REST has the following features

1. It's always a list of items
   So no matter if you get one or many, the resulting JSON is always an array [...]
2. The items are only single-language
   So all the properties will be automatically picked from the language of the current user. 
3. An item is always an object with a list of properties
   Like Name, Birthday, etc.
4. Related items are always an array of IDs
   So the Authors property of a book would be [503, 520, 419]
5. Values are standard JSON types like string, number, etc. 
   Dates are always ISO-standard date formats
6. By default, Id (number) and Guid are also included
7. In edit mode, additional information is included like Modified etc.

Example

[
  {
    "Name": "Web",
    "Description": "<p>We create websites!</p>",
    "Id": 13121,
    "Guid": "1252c52c-30e4-4c9f-8d45-e094160ca251",
    "Title": "Web"
  },
  {
    "Name": "Dev",
    "Description": "<p>Our development unit</p>",
    "Id": 13122,
    "Guid": "c89cb53b-0f7b-441a-9e6c-5467dd9322e9",
    "Title": "Dev"
  },
  {
    "Name": "Eff",
    "Description": "<p>Everything regarding efficiency - like <a href=\"https://sphosting.ch\" target=\"_blank\" rel=\"noopener\">SharePoint</a>, Word &amp; Excel automation, <a href=\"https://azing.org\" target=\"_blank\" rel=\"noopener\">azing.org</a></p>",
    "Id": 13123,
    "Guid": "fa4a1de9-adf5-4e1d-ab70-63281b3e797b",
    "Title": "Eff"
  }
]