FTP site are often called domain.
An FTP site is basically a server connected to the internet. It is popularly used to transfer files of a web site, in order to have such site published over the internet. Also, an FTP site can be used to transfer files, backups, videos, media files, etc.. Not only web site data. The FTP protocol is one of the most popular nowadays. Similarly to the HTTP protocol, FTP is used to transfer files. Thus, the HTTP protocol is usually meant for web pages (hypertext), while FTP is optimized for a large number of files, and bigger filesizes as well.
