Older FTP clients often exposed a chmod option for changing file permissions on a remote server. This was common on shared hosting, but today SSH, SFTP or the hosting file manager is usually safer and easier.
What chmod changes
chmod changes read, write and execute permissions. On web hosting, this is often used for files and directories served by a website.
chmod 644 file.html
chmod 755 public_htmlTypical web-hosting permissions
644: common for normal files755: common for directories600: stricter private files, depending on the server
Avoid unsafe permissions
Avoid making website files or directories world-writable, such as 777, unless your host specifically asks for it and you understand the risk. Wide write permissions can create security problems.
When possible, use SFTP or SSH instead of plain FTP because FTP does not protect credentials or data in transit.