Node.js is not a programming language like Python, Java or C/C++. Node.js is a runtime, similar to Java virtual machine, that converts JavaScript code into machine code. It is , widely used by thousands of developers around the world to develop I/O intensive web applications like video streaming sites, single-page applications, and other web applications.
With Node.js, it is possible to use JavaScript as a backend. With JavaScript already being a popular choice for frontend development, application development around MERN (MongoDB, Express, React and Node.js.) and MEAN (MongoDB, Express, Angular and Node.js) stacks is being increasingly employed by developers.