Put that anywhere in your webpage, and myfile.htm shows up in it's place. The file doesn't have to be a ".htm" file. It could also be a ".txt" file (ie: myfile.txt). So how is this useful? Let's say you have a peice of content that is repeated on many pages of your site (a navigational bar, for example). By saving that content as an individual html file, and using SSI instead to include that content onto those pages, updating that content becomes merely changing that ONE file. The changes is instantly reflected on all pages containing the SSI include command.