Country-based or Geo-based login restrictions function similar to Account Access Lists (ACLs) and can limit logins to your account to IP addresses originating within specific country codes.
This is beneficial in the case of an account compromise where your attacker is situated in a different country than you, or as is commonly the case, they are bouncing off of remote, exotic proxies to conduct their attack.
As with ACLs, Country-based logins can be used in conjunction with your 2-factor authentication settings to allow login from outside your set country list when validated via 2FA. This can prevent a lockout situation when on vacation or otherwise traveling abroad.
All security features are accessed via your account security settings.