With this software, you buy just a few photos. The software will then show them in sequence to each visitor. So when a visitor arrives at your site, they'll see photo 1 on the first page they view, photo 2 on the second page they view, photo 3 on the third page they view, etc. If they get to the end of the sequence, they will start again with photo 1, but since most visitors only visit a few pages of a website, most visitors will see a different photo on each page they visit. Each visitor is tracked separately using "cookies", so the system can handle an unlimited number of visitors.