Node.js is a program that runs JavaScript outside the browser, using the same V8 engine Chrome uses. The language is still JavaScript. What changes is the API: there is no document or window. Instead you get modules for files, TCP, HTTP, and the operating system.
People say “backend in JavaScript” meaning: the same language on the server. It is a good fit if you already know JS from this site’s JavaScript course. It is not required for Anna University labs that use Java or C.
Install
Install the LTS build from nodejs.org. Check:
node -v npm -v
node file.js runs a file. npm is the package manager that comes with Node.
REPL
Type node with no file and you get a prompt. 2 + 2 works. Ctrl+D exits. Useful for trying a snippet; real work lives in files.