The SFTP/SCP service supports various forms of user authentication. These include password, publickey, password OR publickey and password AND public key.
Figure 76
For more information about the other settings on Figure 76, read Adding an SFTP/SCP service
password - User must authenticate with password only.
publickey - User must authenticate with a private key that corresponds with a public key installed on the server.
password OR publickey - User must authenticate with password OR with a private key that corresponds with a public key installed on the server.
password AND publickey - User must authenticate with password AND with a private key that corresponds with a public key installed on the server. This mode is already considered 2-factor authentication (2FA).
See also
Using public key authentication in SFTP/SSH