babel-plugin-transform-es2015-modules-commonjs transforms ES2015 module syntax (import/export) into CommonJS modules. This Babel plugin enables code written using modern ES modules to be compatible with environments that use CommonJS module systems, such as Node.js. It's crucial for projects looking to bridge the gap between newer JavaScript standards and older environments, facilitating smoother transitions and broader compatibility. Developers use it to seamlessly integrate modern syntax into existing CommonJS-based infrastructures.