Node.js is a powerful JavaScript runtime built on Chrome's V8 JavaScript engine, allowing developers to execute JavaScript code server-side. One of its major benefits is the ability to handle multiple connections concurrently without blocking the main thread, making it ideal for building scalable network applications. With an event-driven, non-blocking I/O model, Node.js is particularly well-suited for building real-time applications such as chat applications or live-update dashboards.

Understanding Node.js is essential for modern web development. It leverages JavaScript, a language familiar to many developers, to create fast and efficient server-side applications. Here's why you should consider adopting it:

1. Performance: Its event-driven architecture allows for high-throughput and responsiveness.
2. Community: A large ecosystem of libraries and frameworks like Express.js enhance development speed.
3. Full-Stack JavaScript: This allows developers to use a single language across the entire stack, simplifying the development process.

Node.js has revolutionized the way developers create web applications, particularly when it comes to building scalable applications. With a rich ecosystem of frameworks, it can be challenging to determine which one best meets your project needs. Here are some of the top contenders:

1. Express.js - A minimal and flexible framework that provides a robust set of features for web and mobile applications.
2. Koa.js - Created by the same team behind Express, Koa uses async/await to provide a more modern and cleaner way to write middleware.
3. Sails.js - Great for building data-driven applications; it follows the MVC pattern and is perfect for developing real-time features.
4. NestJS - A progressive framework for building efficient and scalable server-side applications, leveraging TypeScript.
5. Hapi.js - Known for its powerful plugin system, Hapi is ideal for building applications and services that require a robust configuration.

Node.js excels in handling asynchronous programming by utilizing an event-driven architecture. This means that instead of blocking the execution of code while waiting for operations to complete, Node.js allows other code to run concurrently. At the heart of this process is the event loop, which continually checks for events and executes the corresponding callback functions. When an asynchronous function is called, such as reading from a file or making an HTTP request, Node.js delegates this operation to the libuv library, which efficiently manages these operations in the background, freeing up the main thread for other tasks.

One of the core features that enable this asynchronous behavior is the concept of promises. Promises represent a value that may be available now, or in the future, as Node.js processes functions asynchronously. By using promises, developers can write cleaner and more readable code, avoiding the notorious callback hell that can arise from heavy nesting of callbacks. Furthermore, with the introduction of async/await syntax in ECMAScript 2017, handling asynchronous code has become more intuitive, allowing developers to write asynchronous code that looks and behaves like synchronous code, significantly improving code maintenance and readability.