The CommonJS and ES2015 modules we've just looked at are what the Node.js documentation describes as a file module. Such modules are contained within a single file, whose filename ends with .js, .mjs, .json, or .node. The latter are compiled from C or C++ source code, or even other languages such as Rust, while the former are of course written in JavaScript or JSON.
We've already looked at several examples of using these modules, as well as the difference between the CommonJS format traditionally used in Node.js, and the new ES2015 modules that are now supported.
