Secure FTP (SFTP) provides safe authorization, integrity and privacy of data transfer using SSH protocols
SSH (Secure Shell) - a data transfer protocol quite similar to SSL, however there are some differences. SSH was originally intended to exchange messages between Unix-based servers and requires identification on both sides. Moreover, SSH supports logical channels over already established sessions and uses so-called "key pairs" (instead of certificates) for identification.
Unlike certificates, key pairs are generated by a client, not by a Certificate Authority. To verify the identity of a key pair, trusted storages are used. Such storages house client/server public keys, and more. Which storages can be trusted and which cannot are determined by a client.