Two-factor authentication (2FA) enhances security for online accounts by requiring users to provide two forms of verification before accessing their accounts. Typically, this involves something the user knows (like a password) and something the user has (like a mobile device for a one-time code). This additional layer of security significantly reduces the risk of unauthorized access, even if a password is compromised. By implementing 2FA, users create a more robust security posture, making it more challenging for potential attackers to gain access to sensitive information or accounts.