Alf - you are to be congratulated and thanked, very much. You really hit the nail on this one. Cheers!
You can use it to append the name of your website in every page title. The site name can be in front of or behind the page title. There's even a homepage option that is useful to avoid "doubling" your site name in the page title. Well considered.
It's necessary for SEO and it works great.