Node.js authentication involves securing Node.js applications by verifying the identity of users or clients. This process typically includes implementing strategies to manage user login sessions, encrypt passwords, and ensure data security as it travels between server and client.

The Node.js environment can integrate various authentication mechanisms, such as JSON Web Tokens (JWT), OAuth, or session-based authentication using cookies. JWT, for instance, allows stateless authentication, where the server does not need to keep a record of tokens. OAuth is often used for allowing users to log in with third-party accounts like Google or Facebook. Session-based authentication stores the user state on the server, which can be more traditional but requires careful handling of session data to ensure scalability and security.

Developers learn to use middleware in the Node.js Express framework to handle authentication processes and protect routes. They also utilize secure password hashing libraries like bcrypt to safeguard user credentials. By mastering Node.js authentication, developers ensure that sensitive information and user data are securely managed, which is a critical aspect of building trustworthy applications.