blog (abbrev. Web Log) is a type of website that allows its owner to update the content dynamically without any expert knowledge of website design or programming. Blogs originated as a sort of online diary that could be shared with the world. The popularity of blogging has grown rapidly and blogs are now being used to promote businesses of all sorts.
When you have a blog in your website that you update on a regular basis, you're adding fresh content to your website. Each time the search engines visit your site, they'll find the blog and take note of the great content that is continually arriving.
Websites such as CNN.com, ESPN.com, and the like do very well on the search engines, not just because of who they are, but because they have boundless numbers of pages of content that are updated on a daily basis. Your site may not need to compete with CNN.com, but there's something to be learned from their success. By updating your website on a regular basis, you give the search engines fresh content to return to their searchers, which is why search engines exist at all. When the search engines identify your site as a source for up-to-date information, you will automatically do better on the search engines than sites whose content hasn't been added to since the day the site was launched. Adding additional pages will also give the optimizers more material to work with.
Blogs aren't for everyone. If you and your practice can't commit to updating the blog at least twice a week, then a blog probably isn't what you need. An RSS Feed might work better. Blogs that do not get new entries on a regular basis are simply a waste of time because the search engines will not find the new content that is so crucial. At that point, you might as well have not spent the money to add a blog.