Authentication methods is a report that gives insights into Multi Factor Authentication configurations per user.
You will see the default MFA method used by each individual and should consider to run MFA campaigns to ensure that all your end-users uses a secure way to authenticate to your solutions and data. You will also see all MFA methods configured and available per user.
Worst case scenario is if someone guess the correct password to a member account haven't registered MFA and have not self service password registered. Most likely someone will configure MFA according to policy and start consuming your solutions and data.
You will find these users by selecting MFA registration complete = FALSE and SSPR Registered = FALSE