## What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format used to exchange structured data between systems. It originated in JavaScript but is now language-independent and supported by virtually every modern programming language.

A JSON document is built from a small set of building blocks:

- Objects: unordered collections of key-value pairs wrapped in `{}`
- Arrays: ordered lists of values wrapped in `[]`
- Primitives: strings, numbers, booleans, and `null`

Here is a minimal example representing a single user record:

```json
{
  "id": 42,
  "name": "Ada Lovelace",
  "active": true
}
```

The core value types and their typical use cases are summarized below.

| Type | Example | Typical use |
| --- | --- | --- |
| string | `"hello"` | Names, labels, free text |
| number | `3.14` | IDs, counts, measurements |
| boolean | `true` | Flags, feature toggles |

JSON is widely used for REST API payloads, configuration files, and persisting application state because it is easy to read, easy to parse, and supported everywhere.