Find more about JSON on Wikipedia: https://en.wikipedia.org/wiki/JSON.
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JSON's basic data types are:
Number: a signed decimal number that may contain a fractional part and may use exponential E notation , but cannot include non-numbers such as NaN. The format makes no distinction between integer and floating-point. JavaScript uses a double-precision floating-point format for all its numeric values, but other languages implementing JSON may encode numbers differently.
String: a sequence of zero or more Unicode characters. Strings are delimited with double quotation marks and support a backslash escaping syntax.
Boolean: either of the values true or false
Array: An ordered list of zero or more values, each of which may be of any type. Arrays use square bracket notation with comma-separated elements.
Object: an unordered collection of name-value pairs where the names (also called keys) are strings. Objects represent associative arrays [8], where each key is unique within an object. Objects are delimited with curly brackets, and use commas are used to separate each pair, while within each pair, the colon ':' character separates the key or name from its value.
null: an empty value, using the word null
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See JSON in Display Pattern Editor
You find the JSON in the display pattern editor in JSON preview: 
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kind: shows the type of content, e.g., ContentDoc for content items or ListItemDoc for list items.
fileTransferId: shows all assigned contentPermissionSets
ownerTokenId: shows the
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ID of the owner
contentType: shows the type of content, e.g., File or Virtual
backup information
contentSchemaId: is the underlying schema of type file type or virtual type with the assigned layers.
In data, you find all available metadata values from the item
brokenReferenceIds, RelationTargetIds, and IndirectReferenceIds are for system checks to ensure data integrity. You can use those fields to check for any broken references in the system to fix them.
lifeCycle: is the state of the item, whereas inactive items are no longer available in the system
id: the ID of the item, which is also shown in the URL when opening the item in the item detail view
docType: refers to the kind and the corresponding index in the database, e.g., ContentDoc or ListItemDoc
audit: shows information about creation and modification.
See JSON in Chrome Developer Tools
You can see the JSON of an item by { opening up the item detail view and check checking in the developer tools (Chrome F12) in the network the response for the corresponding item, shown as id: 
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