Imagine a very large traditional filing cabinet as large as a room filing cabinet that is what an FTP site is like. In a filing cabinet, the clerk can label and organize files depending on how he wants it or the system he implements. He also dictates which files can be accessed freely and which files are off limits and available only to a chosen few.
In an FTP site, a UserID and Password is the key that opens this giant filing cabinet. The creator of the site has the power who to grant access to what information. Some sites have open access to everyone with a valid UserID and Password. For open sites, the UserID is “anonymous” and the Password would be your e-mail address. However, for restricted sites, there is an assigned UserID and Password unique to every qualified user.