FTP(S) (explicit SSL/TLS, or no SSL, Port 22)
This is the most commonly used option. If your FTP server runs on Port 22, then this is the correct option. We will negotiate SSL/TLS connectivity as a preference if it's available from the remote server.
If encryption is not supported by the remote server, standard FTP will be used.
FTPS (implicit SSL, Port 990)
This option uses port 990 for implicit SSL FTP transfer. This option is not commonly used, however may be required by some servers.
This option is rarely used - files are transferred over the SSH protocol using the SFTP standard, rather than FTP(S). When using this option, your SSH SFTP session must be CHROOTed into the backup directory, as the import tool will try to download the root (/) directory from the SFTP servers perspective.