npm-which is a Node.js module that enhances the standard which command for finding executable binaries, specifically within the context of npm's node_modules/.bin directory. It intelligently searches for executables installed locally by npm packages before falling back to the system's PATH. This guarantees that when you're working within an npm project, you'll find the version of a command intended for that project, avoiding potential conflicts with globally installed versions. It handles platform differences gracefully and provides a reliable way to locate executables in a Node.js environment.