CGI stands for Common Gateway Interface. Meaning, having rotated banner ads, time dates, form to mail gateways, guestbooks, discussion board, and more.
Most servers have the capability to put CGI scripts onto their machines.
But some don't, can't configure it, or other problems. That's where X-Point CGI comes in. Very easy to do. More CGI scripts will be added every month or so. This script rotates your advertisements and keeps a count of impressions and click-throughs for each advertisement shown, allowing you to bill your advertisers accordingly.