Content quality is made up of three primary factors, authority, utility and presentation.
It defines authority as if they can trust the content.It is not just about the links pointing to the page but also about how established the web site and web page is.
Page written is useful and detailed enough to the searcher for them to accomplish their task. Is it detailed enough for the typical searcher also prefers to see videos, images and graphs on the page – those are signals of utility and content quality.
A factor that may harm the content quality is re purposed or “recycled” content.
This is about making sure the content on the page is easy to find and easy to read. If you have ads in the way, distracting and unrelated ads or the content is hard to find, this can hurt your content quality score. Google+