The bold tag can be used to make words appear in a bolder font on the web page.
Webmasters may use the bold tag to make certain words in their content stand out more, increasing the likelihood of users acknowledging that word whilst quickly scanning the page.
It’s been widely discussed in the search industry that wrapping the tag around important keywords will result in the search engines placing slightly greater weight on those words than regular text. Therefore a lot of webmasters tend to apply bold tags to the keywords that they’re looking to rank for in their content, as they think it will increase their search engine positioning for that query. Some SEO’s strongly believe that these tags won’t help your SEO efforts at all, there are lots of mixed opinions on the subject.
This hasn’t yet been confirmed by Google, we can only guess at this point.
The bold tag can be used for both user experience and SEO, however, as the bold tag hasn’t yet been officially confirmed to be part of the ranking algorithms at Google, I’d suggest to only implement this tag if it’s beneficial for the user.
Below are some examples of using the tag:
<strong>This is a bold tag</strong> <b>Here is another bold tag</b>
In terms of SEO, there is no difference between the strong tag and b tag for emphasis on certain words of text, both are treated exactly the same in Google’s ranking algorithms, according to Matt Cutts.
Both of these tags from a user experience perspective do the same thing: render the text bold.