Two-factor authentication is an important security measure that you can add to online accounts that support this feature. It sends a one-time-passcode (OTP) to your phone via SMS, an authenticator app, or a hardware security key.
Two-factor authentication just means that you need a second factor to log into an account besides your username or email + password combo. It makes your account more difficult to hack into, although SMS authentication isn’t as secure as an authentication app.
Although some websites may ask you to use a specific authenticator app like Google, it really doesn’t matter because they all do the same thing. The main way to add authentication to your account is to use the app to scan a special QR code. Once that’s done, you’ll see a six digit code in the app that changes every 30 seconds.
Nowadays, most password managers have built-in support for authentication, like 1Password and Bitwarden. But there are dedicated apps, too.
All of these apps are free to download, and FreeOTP is free and open source.