Node.js is a JavaScript runtime environment: This means that in addition to the “normal” use case of JavaScript being executed at the client (usually in the web browser), Node.js is executed on the server side.
This can be used to implement custom web servers, for example. A well-known technique for which Node.js is used is RestAPIs. A RestAPI is a server-side interface, which together with the frontend represent a complete web application. The client sends a HTTP request to the RestAPI, which then e.g. writes/reads data into a database or sends a chat message to other active participants of the web application via a socket connection.
Interested? Have a look around!
