The main difference between FTP (File Transfer Protocol) and SFTP (SSH File Transfer Protocol) lies in their security mechanisms and the way data is transmitted.

1. Security: FTP does not provide inherent encryption for data transmission. This means that files, commands, and login credentials are sent in plain text, making FTP vulnerable to eavesdropping and data interception. On the other hand, SFTP uses SSH as the underlying protocol, which provides encryption and secure authentication. All data transferred via SFTP, including file contents and login information, is encrypted, ensuring confidentiality and integrity.

2. Authentication: FTP primarily relies on username and password authentication, which can be less secure since passwords are transmitted in plain text. In contrast, SFTP uses SSH's authentication methods, including password authentication and public key authentication. This offers stronger authentication mechanisms and helps prevent unauthorized access to the server.

3. Portability: FTP is widely supported and available on various operating systems. However, the FTP implementations may differ slightly, leading to compatibility issues between different servers and clients. SFTP, being based on SSH, is more portable as it can run on different platforms, including Unix-like systems, Windows, and macOS, with consistent behavior across implementations.

4. Connection: FTP uses separate control and data connections. The control connection is established for issuing commands and managing the FTP session, while a separate data connection is established for actual file transfer. In contrast, SFTP uses a single connection for both control and data transfer. This simplifies network configurations and firewall setups.

5. Default Port: FTP traditionally uses port 21 for control connections and dynamically assigned ports for data connections. On the other hand, SFTP typically uses port 22, which is the default port for SSH.

6. Passive Mode: FTP supports passive mode, where the client initiates both control and data connections. This is useful when the client is behind a firewall or NAT device. SFTP also supports a similar passive mode, but the way it operates is different due to the underlying SSH connection.

Overall, the key distinction between FTP and SFTP lies in their security features. SFTP provides secure file transfer capabilities by leveraging SSH for encryption and authentication, ensuring that data remains protected during transmission. If security is a concern, SFTP is generally recommended over FTP.