File and Directory Names

• So, why is it the node_modules folder, but package.json file?
• Why not node_packages or module.json?

The package.json file defines the package. (See "What is a package?", above.)

The node_modules folder is the place Node.js looks for modules. (See "What is a module?", above.)

For example, if you create a file at node_modules/foo.js and then had a program that did var f = require('foo.js'), it would load the module. However, foo.js is not a "package" in this case, because it does not have a package.json.

Alternatively, if you create a package which does not have an index.js or a "main" field in the package.json file, then it is not a module. Even if it's installed in node_modules, it can't be an argument to require().