What does "two-factor authentication" (2FA) require?

Two-factor authentication (2FA) is a security process that requires users to provide two different forms of verification before accessing an account or service. This approach significantly enhances security by combining two distinct elements: something the user knows (like a password) and something the user possesses (like a smartphone app for generating a code, or a hardware token).

The essence of 2FA lies in its dual nature, which helps guard against unauthorized access even if one of the factors (such as a password) is compromised. For example, even if a hacker manages to obtain someone’s password, they would still need the second piece of verification to gain access, thus adding an additional layer of security.

The other options suggest inadequate or overly simplistic security measures. One form of verification, verification from multiple users, or only simple password input do not align with the core principle of 2FA, which aims to require that both factors are utilized for authentication.