Learn more about the Personal Vault, a protected area in OneDrive that you can only access with a strong authentication method or a second step of identity verification, such as your fingerprint, face, PIN, or a code sent to you via email or SMS. Your locked files in Personal Vault have an extra layer of security, keeping them more secured in the event that someone gains access to your account or your device.

Read more about the OneDrive Personal Vault: https://www.microsoft.com/en-u....s/microsoft-365/blog

As full-disclosure, I work at Microsoft as a full-time employee.