Two-step verification allows you to sign into accounts with something you know (your password) and something you have (a code sent to your phone) That means that even if your password is guessed or phished, an attacker will find it difficult to access your account as (hopefully) they wont also have your phone. In this guide, I will show you how to enable login approvals, aka 2SV, on your Facebook account. It works very similar to Google Authenticator in that its codes are time-sensitive.”]
Source: https://grahamcluley.com/protect-facebook-account-2-step-verification-2sv/