The most common additional verification is an authentication app on your phone: when you log in, a verification is sent to the authentiator app, and your verify it's you by pressing a button in the app or entering a code sent to the app.
Authenticator apps we recommend are:
Please use the authenticator apps we recommend, as not all authenticator apps are equally secure. These authenticator apps collect personal information: Microsoft Authenticator (collects and shares information with Microsoft), Authy (collects and shares information with Google).
An even more secure, but less convenient, verification method is Hardware security keys. You can read all about hardware security keys at privacyguides.org.