What is Node.js primarily known for?

Node.js is primarily recognized as a runtime environment for JavaScript. This means it provides the infrastructure necessary to execute JavaScript code outside of a web browser. Traditionally, JavaScript was primarily used for client-side scripting in web browsers, allowing developers to create dynamic and interactive web pages. However, Node.js extends the capabilities of JavaScript by enabling developers to run it on the server side, thereby allowing for the creation of scalable network applications.

Node.js is built on the V8 JavaScript engine, which is developed by Google for Chrome, providing high performance for executing JavaScript code. It is particularly well-suited for building applications that require rapid I/O operations, such as web servers, due to its non-blocking, event-driven architecture. This makes it a popular choice for developing real-time applications, APIs, and microservices.

In contrast, the other options represent different concepts that do not align with the primary function of Node.js. A web browser is a software application for retrieving and displaying web content, while a programming language is a formal system for instructing a computer. A styling language, like CSS, is used for designing the aesthetic elements of web pages rather than for executing logic, making these choices distinct from what Node.js offers.