FTP"S" vs "S"FTP

Both, SFTP and FTPS share the "FTP" part, which stands for File Transfer Protocol, the  protocol which is designed to transfer large files within a network. But as it lacks security, a newer version is released and called FTPS, which is FTP over SSL.

As you may know, everything comes with SSL, means a "secure" thing. FTPS uses certificates to secure the data on the way, when downloading or uploading.
FTPS uses couple of port numbers. The default port 21  is used for authentication and passing commands.  However, every time a file transfer request (get or put) another port number needs to be opened (990 is the default).

So how FTPS differs from SFTP?
Not to mentions, the two protocols confuse us, because they look like the same when we think the letter "S" stands for "Secure".
To clear things up, as mentioned the "S" in the FTPS refers to SSL. However the one in the SFTP, refers to SSH ;)

Still confused? if you can remember, SSH is the protocol that we use when connecting remotely (and securely) to a remote system, such as Linux box or a Cisco router. SFTP stands for FTP in SSH, and refers to the ability of SSH protocol to transfer data when already connected to a remote box.
In this case FTP is under the umbrella of SSH and uses whatever protocol SSH uses (default is 22).