A blog is a web site. There is no difference really, and with this type of site you can update the site yourself easily from any browser from anywhere. A “custom website” of yesteryear – was often difficult to update. And very expensive. Today – easy.
I have been creating websites since the web became a way to share information in around 1993. Until a few years ago we used complicated web design software that required skills and patience to create a site. Not too many business people had the time nor interest to acquire the software and learn how to use it. So we became “webmasters”. Web geeks. These days, with WordPress as the new standard – it is much easier to set up a web site for the average business person without too much learning. That’s a good thing, but it still takes time and some knowledge.