Header tags and SEO.
The bolded text above is really a header tag. Using Header tags tells the search engine what "words" are important in the context of your page.
Consider <h1>,<h2>,<h3>, etc.. to be the way that you highlight important keywords.
Different browsers interpret the Header tags in different ways. The format for them is always the same though: <h4>Header tags and your rankings.</h4>
There are several different pre-set sizes for header text using tags. They range from H1, to H6. You should use them to highlight your chosen keywords, and try to avoid fluff words - remember, you are writing for people not machines, so if you need a pronoun -- use it.
In other segments of this website we have used blackbeltdomain.com as an example. Go check out the bolded text there and see how they are using Header tags to stand out for their chosen keywords.
Your rankings will suffer with out the proper use of Header tags, so don't leave them out of your planning stages of search engine optimization.