'Node.js' is a revolutionary open-source, cross-platform JavaScript runtime, transforming back-end development since its creation by Ryan Dahl in 2009. Running on the V8 engine, Node.js extends JavaScript's capabilities beyond the web browser, becoming a crucial tool in modern web development, particularly for building scalable network applications.

Node.js is adept at crafting scalable network applications, handling multiple connections simultaneously with ease. Its event-driven, non-blocking I/O model contributes to its efficiency, making it an ideal choice for real-time, data-intensive applications across distributed devices.

A groundbreaking aspect of Node.js is the consolidation of JavaScript for both server-side and client-side scripting. This harmonization streamlines the development process, enabling the use of a single programming language across the entire application, thus enhancing development efficiency and uniformity.

Node.js comes with an extensive array of JavaScript modules, significantly simplifying the development of web applications. Its package ecosystem, npm (Node.js package manager), is renowned as the largest collection of open-source libraries globally, offering a multitude of tools and modules for developers.

In conclusion, Node.js has been a game-changer in the realm of web application development. Its capacity to handle asynchronous operations, scalability, and the advantage of a unified JavaScript environment across the full stack make it an essential element in contemporary web application development.