FTP, FTPS over SSL short or FTP over TLS is a method to encrypt the file transfer protocol (FTP), which is described in RFC 4217.
In contrast to SFTP FTPS is a combination of FTP and Transport Layer Security (TLS).
The encryption of FTP is complex, because this protocol requires at least two separate connections. FTPS therefore stipulates that the payload is not necessarily encrypted and after authentication, the encryption can be omitted. The extent to which the encrypted FTPS, also depends on the respective server and client.
Several dozen clients and servers as well as some proxies support FTPS. For FXP over TLS example, there are SSCN.