Node.js · Runtime · Fresh / Intern · Comparison
What is the Node.js runtime, and how does it differ from browser JavaScript?
Short Interview Answer
Node.js is a V8-based JS runtime plus libuv for async I/O, with OS APIs (fs, net, process) instead of DOM/window.
Detailed Explanation
It shares the language and much of ECMAScript with browsers but exposes different globals and modules. Single-threaded JS drives concurrent I/O via the event loop. Understanding the runtime boundary (JS vs native addons vs OS) is foundational for performance and debugging interviews.