Why is my FTP server not uploaded to my website?

I am thinking I need to contact my webhost because I am stumped. I am new to this website stuff, but when I preview what my site looks like on my ftp server it looks one way (I changed the background) but my website itself does not look the same. I originally made my website on a builder and now that I am getting better at it I started using FTP, but all my changes in FTP don't show up on my site. Help please!! :) :)