What are modules in JavaScript?

Modules in JavaScript refer to reusable pieces of code that encapsulate specific functionality and can be imported or exported across different files or scripts. This modular approach allows developers to break down complex applications into smaller, manageable, and organized pieces, facilitating better code maintenance, reuse, and collaboration among developers.

By exporting a module, you can make its functionality available to other modules or parts of your application. Conversely, you can also import modules into your code to access the functionalities they provide. This system encourages separation of concerns and helps keep code organized and easy to understand.

The other options focus on different concepts within programming. Basic data structures relate to the organization of data, events pertain to the handling of user interactions, and specific classes defined in ECMAScript deal with object-oriented programming. However, none of these accurately describe what modules are or how they function within the JavaScript ecosystem.