A Node.js Native Add-on is a compiled binary module written in languages like C or C++ that extends Node.js functionality beyond what is possible with pure JavaScript. These add-ons interact directly with the underlying operating system or hardware, enabling high-performance operations such as cryptography, image processing, or access to system-level APIs. Native add-ons are loaded into Node.js using the require() function, just like regular modules, but they run outside of JavaScript’s usual restrictions and can introduce additional security risks if not properly managed. Developers use tools like node-gyp to compile and integrate these add-ons into their Node.js applications.