When you are working with JSON data in Android, you would use JSONArray to parse JSON which starts with the array brackets. Arrays in JSON are used to organize a collection of related items (Which could be JSON objects).
For example: [{"name":"item 1"},{"name": "item2"} ]
On the other hand, you would use JSONObject when dealing with JSON that begins with curly braces. A JSON object is typically used to contain key/value pairs related to one item.
For example: {"name": "item1", "description": "a JSON object"}
Of course, JSON arrays and objects may be nested inside one another. One common example of this is an API that returns a JSON object containing some metadata alongside an array of the items matching your query:
{"startIndex": 0, "data": [{"name": "item 1"},{"name": "item2"} ]}