Two-factor authentication is a secondary authentication method for logging into email, social media, banking or corporate accounts. Most, if not all, major email, banking and social media platforms offer two-factor authentication free of charge. When you log in from an unrecognized computer or mobile device, the service provider sends a text message to your cell phone. This ensures no one can access your account with only your password. While this is not foolproof it will add a layer of security.
Check out this site for the instructions on enabling two-step authentication on most major sites: twofactorauth.org