JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write and easy for machines to parse and generate. It 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.

A JSON formatter is a tool that takes JSON input and formats it to be more readable for humans. This usually involves adding indentation and line breaks.

Most JSON formatters work by pasting your JSON into a text box and clicking a button to format it. The formatter will then display the formatted JSON.

If your JSON isn't formatting correctly, it's likely that there's a syntax error in your JSON. JSON has strict rules and even small mistakes like trailing commas or missing quotes can cause errors. A good JSON formatter will tell you where the error is.

A JSON object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).

A JSON array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).

A value can be a string in double quotes, a number, a boolean (true or false), null, an array, or another object. This makes JSON a very flexible data format.

No, JSON does not support comments. It was designed to be minimal, portable and simple, so it does not include the complexity of comments. If you want to include comments with your data, you'll need to include them as data within your JSON.

In JavaScript, you can use the JSON.parse() function to convert a JSON string into a JavaScript object. For example: var obj = JSON.parse('{"name":"John", "age":30, "city":"New York"}');.