FTP and SFTP: definition
FTP and SFTP are two protocols for transferring files between a computer and a web server; SFTP encrypts the connection, unlike plain FTP.
A difference that matters for shop security
FTP (File Transfer Protocol) sends files, but also the username and password, in plain text over the network. SFTP (SSH File Transfer Protocol) routes this traffic through an encrypted tunnel over SSH, which prevents credentials from being intercepted. For a shop that handles sensitive files (theme, modules, configuration files containing database access details), transferring over unencrypted FTP exposes this information to anyone listening on the traffic, for example on public Wi-Fi.
That's why most hosts now offer SFTP by default. In practice, usage stays the same in a client like FileZilla: only the protocol and connection port change, with SFTP using port 22 (SSH) instead of FTP's port 21.
Frequently asked questions
How do I know if my host offers SFTP?
Do FTP and SFTP give access to the same files?
Is SFTP enough to fully secure access to a shop?
Describe your need in one minute
A few targeted questions so I can reply with an estimate rather than another questionnaire.