Which of the following correctly describes the 401 HTTP response?

The 401 HTTP response status code specifically indicates that authentication is required to access the requested resource. When a client makes a request to a server and the server determines that the client needs to authenticate itself in order to proceed, it will respond with the 401 status code. This response typically includes a "WWW-Authenticate" header field that provides information on how to authenticate properly.

This mechanism is part of the HTTP authentication framework, where the server can enforce restrictions on access to content based on the authentication status of the client. If a client receives a 401 response, it should prompt the user for credentials, which it can then use to repeat the request with the necessary authentication information.

Understanding this status code is crucial for developers when handling user authentication and authorization in web applications, as it directly relates to securing resources and maintaining access controls.