Node.js is a JavaScript runtime environment that enables server-side programming and is known for its scalability, ease of learning, and the ability for developers to use JavaScript for both front-end and back-end development. While it offers high performance and a supportive community, it also faces challenges such as an unstable API and a lack of robust library support. Despite these drawbacks, the advantages of Node.js often outweigh the disadvantages, making it a popular choice among developers.