FTP or SFTP: the difference and why it matters
Both transfer files to your server. Only one does it securely.
FTP
Everything travels in the clear: your username, your password and your files. On a shared network that means anybody on that network can read them.
SFTP
The same thing, but encrypted. Same login, different port, and nothing travels readable.
Why this matters more than people think
An intercepted FTP password gives full write access to your site. That is how malicious code most often gets injected — not through a hole in your CMS.
What to do
Switch FTP off entirely if your hosting allows it. Use SFTP everywhere, and change your password if you have used plain FTP in recent years.
One account per person
A shared login means you cannot revoke access for one individual. Create separate accounts and limit them to the folder they need.