Content targeting is a different form of paid inclusion than the normal keyword based search queries. The difference between content targeting and other forms of paid inclusion is that content targeting involves matching not just keywords that are used in a search query with advertisements, but with matching the actual contents of web pages with search queries.

This is a good article for small publishers. The article discribes the challenge of measuring ROI for small publishers and some solutions. However it doesn't really explore the ROI metrics for measuring success.

Native advertising is a web advertising method in which the advertiser attempts to attract attention by providing valuable content in the context of the user's experience. Similar conceptually to an advertorial, which is a paid placement attempting to look like an article, a native ad tends to be more obviously an ad while still providing interesting or useful information.[1] The advertiser's intent is to make the paid advertising feel less intrusive and, therefore, increase the likelihood users will click on it