A blog is a regularly updated website, typically one run by an individual or small group, that is written in an informal or conversational style.
One common way affiliates deliver their content is through blogs. These niche style blogs gain authority and trust as more and more content is added. So this is essentially how you will build an "authority niche site".
There are actual platforms already built that allow you to set these up extremely fast. Blogs allow you to deliver multiple articles and content (and landing pages) all on one website. All of our affiliate niche blogs are built through the use of a program called WordPress. (There are many others but WordPress is very easy and popular and FREE)