A static website is one in which all of the content is pre-generated. This blog is a good example of that because all of the HTML files are built locally and then uploaded to the server (using RSync).
The usual way that websites work is by having a content management system that generates pages on the fly (e.g. Wordpress, FlatLaw). Although there are a lot of factors that go into choosing a dynamic vs. static website, an important advantage for a static site is security.
A static website won't suffer from vulnerabilities due to SQL injection, a very common attack vector. If you have a law firm site, you should consider switching to a static model. There are plugins for Wordpress (and other platforms) that can accomplish this. Your site will be more secure and probably much faster.