Multi-Factor Authentication (MFA) is an added security layer to applications, making it harder for hackers or impersonators to steal and use user credentials. MFA requires two types of identification: something the user knows (password), and something the user has (device). Passwords are inherently insecure, so adding a second layer of authentication significantly improves account security. MFA is crucial for businesses as it prevents devastating data breaches that can cost millions. It's especially important for consumer-focused apps handling sensitive data like banks and credit cards. Implementing MFA involves significant backend changes and frontend adjustments to accommodate the additional authentication steps.