Content management systems predate blogs, but essentially serve the same purposes: efficiently managing and organizing a website using templates and databases.
CMS’s are typically used for web sites with content that isn’t updated very frequently. Blogs are essentially content management systems for constantly that is updated frequently. Consider this very web site. There are pages (“about us,” “service,” “contact”) that aren’t updated frequently along with a blog that offers company news and helpful hints and tips for small businesses. All of this is powered by a platform called WordPress.