In the last slide, I mentioned that search engines needed to be able to find your blog, index it, understand it, evaluate it, and rank it. Finding it and indexing it are usually pretty simple. Presumably you'll get the word out about your blog somewhere, with a link to it, and search engines will see the link, follow it, find your blog and proceed to index it. And since WordPress pings by default, search engines will find you.
But your job is to help the search engine UNDERSTAND what your blog posts are all about. The easiest way to accomplish that goal is to simply tell the search engines what each post and page is about. If your post is a recipe for Cherry-Filled Chocolate Cake, you would probably want to actually use that phrase along with the word 'recipe' within the prominent places of your post. If you only ever call it Yummy Yum Yum, the search engines may have a hard time recognizing it as a cherry-filled chocolate cake recipe.