it varies for different services but in the case of google, you need to set up 2 factor authentication in your google account (under security and passwords etc). As part of that set up process it will show you a qr code OR a long string of numbers and letters like i described above - this is the token you need. You then enter that code into an autheticator app (google have their own but others like the watch version work too) to set it up... basically, from that token the app generates a short lived 6 digit code thats vaild for 30 seconds... next time you log into a google service on a new device or app, it asks for both your password and a temporary authentication code - it means you have some protection if your password is ever compromised. Its a pain and not 100% fool proof but significantly raises the security on your account.
Google 2 factor authetication for google accounts and see if its something you want use BEFORE setting it up (if you loose the authenticator, you need to make sure you have your recovery options set up properly or you will loose access to your account).
