The strongest passwords are the ones that are truly random, that you could never remember. That's why you need a password manager. We recommend LastPass Premium (there's a family option too and you can combine with a yubikey for best of breed security). Download here and receive a free month of LastPass Premium.
Premium membership is USD $2/mth and family membership is USD $4/mth (includes 6 users)
Second Factor Authentication (2FA)
Multifactor / second factor (2FA) are different names for the same thing. It's a second way of verifying you as you log in to important sites (like email, banking or password managers) so even if your password has been compromised without 2FA (eg a second factor of authentication) the hacker can't access your accounts. There are lots of ways to do this (eg hardware such as a Yubikey) or SMS / Authenticator Apps.