Thin content is content that has little or no value to the user. Google considers doorway pages, low-quality affiliate pages, or simply pages with very little or no content as thin content pages.
But don’t fall into the trap of just producing loads of very similar content: non-original pages, pages with scraped and duplicate content, are considered thin content pages too. On top of that, Google doesn’t like pages that are stuffed with keywords either.
Google has gotten smarter and has learned to distinguish between valuable and low-quality content, especially since Google Panda.
As we established, thin content means low-value content. Because of that, when looking to avoid any type of thin content penalty, your goal is to make your pages stand out in both the user’s and Google’s eyes in a positive way.