SSO stands for Single Sign-On and allows user to login with tools you use everyday.
For example, you can log in Signitic with your Google account or your Office 365 account.
This process uses the security system of the third party application and so can use more advanced security mesures like Double Factor Authentification.
You can enable this option in your security settings :
This option, when enabled, will disable basic connection with email/password. So it will ensure that your Signitic administrators use SSO connection when login.
This will increase then the global security of your accounts and informations.