This is like a link wheel, except that you own all the sites that you’re linking together. You may link together a series of smaller niche sites, with each smaller site linking to your main site.
Building a mini-net is just a way to improve the ranking of your website in search engine results. A mini-net is a set of websites that is owned by the same person or organization. Moreover, these websites are linked together. However, take note that they should not be linked all together and there should be no loop of links because this would be un-natural and Google or other search engines will definitely realize that these mini-net sites are all grouped together and this might be the reason for them to ban your mini-net sites.