cgi is the command that tells fossil it is running as a web-page supplier for an external http server. (For you web-miesters, the "cgi" is actually unnecessary if your web environment is set up in a normal fashion.)

This is the command you will probably use if you want to make a moderate-to-high hit rate public repository (like the fossil project's self-hosted repository) but you'll be using it in the shebang line.

If you need lower level access to the pages fossil generates, you'll want to look at the http command.

See also: fossil http, Concepts (setting up a server), Reference