JSON stands for JavaScript Object Notation. It 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 based on a subset of the JavaScript programming language and is often used as a data format for web applications and APIs.

JSON data is represented as key-value pairs, where the key is a string and the value can be a string, number, boolean, array, or another JSON object. For example, a JSON object representing a person might look like this:

{ "name": "John Doe", 
"age": 30, 
"isMarried": false, 
"hobbies": ["reading", "hiking", "coding"], 
"address": 
    { "street": "123 Main St", 
    "city": "Anytown", 
    "state": "CA", 
    "zip": "12345" 
    }
 }

JSON has become a popular data format for web applications because it is easy to work with and is supported by many programming languages and frameworks.

To implement JSON for an API response, you will need to generate JSON-formatted data in the programming language you are using for your web application. Here's a general overview of the steps involved:

1. Define the data structure: Define the data structure for the API response in your web application. This can include any data fields that you want to include in the response.

2. Serialize the data: Serialize the data from your web application into a JSON string using a JSON serializer library. Most modern programming languages have built-in or third-party libraries for JSON serialization.

3. Set the response headers: Set the response headers of your API to indicate that the response data is in JSON format. This can be done by setting the "Content-Type" header to "application/json".

4. Send the response: Send the JSON-formatted data as the response to the API request.

Here's an example in C# using .NET Core and the built-in System.Text.Json library to generate a JSON-formatted API response:

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Text.Json;

[ApiController]
[Route("api/[controller]")]
public class ExampleController : ControllerBase
{
    [HttpGet]
    public IActionResult Get()
    {
        // Define the data structure
        var data = new Dictionary<string, object>
        {
            { "name", "John Doe" },
            { "age", 30 },
            { "hobbies", new string[] { "reading", "hiking", "coding" } }
        };

        // Serialize the data to a JSON string
        var json = JsonSerializer.Serialize(data);

        // Set the response headers and content
        Response.ContentType = "application/json";
        return Content(json);
    }
}

In this example, the ExampleController class defines a single HttpGet method that returns an example JSON-formatted response. The Dictionary<string, object> type is used to define the data structure. The JsonSerializer.Serialize method is used to serialize the data to a JSON-formatted string. Finally, the response headers are set to indicate that the response data is in JSON format, and the JSON-formatted data is returned as the response to the API request using the Content method.