Wiki api property question

I have been searching and reading many posts on FCC and other’s code, but I still can’t figure it out…
please help.

var url = "" + searchTerm + "&format=json&formatversion=2&callback=?"; // url to look for using the search input by the user $.getJSON(url, function(data) { var arTitle = data[1]; var arUrl = data[3]; var arDesc = data[2];

I saw that other’s codes contain arTitle, arDesc and also data[1], data[2], my question is where to check it? How can I find what the available objects I can use?
The weather api property is easy to read and understand.,… but I have tried to look at API sandbox and still don’t have any clue…

This is what I got from the API sendbox
{ "batchcomplete": "", "query": { "pages": { "26537": { "pageid": 26537, "ns": 0, "title": "Rose", "contentmodel": "wikitext", "pagelanguage": "en", "pagelanguagehtmlcode": "en", "pagelanguagedir": "ltr", "touched": "2017-10-30T00:47:29Z", "lastrevid": 798792556, "length": 19650 } } } }

Please help me~~~~