This extension provides an additional filtered view on your browser history. It works like this: Say you are on the website http://www.example.org/page1.html and you click on "Domain: Back" - which is the new menu entry provided by this extension - your browser history is filtered to only contain those entries that refer to something on http://www.example.org. Based on this filtered view, you are then taken back one page.
The usefulness of this function might not be obvious at first glance, but this very simple technique can be used for several helpful tricks, including the main reason this extension was written: Say you have been reading through the archives of your favourite blog and now - at some later point - you want to continue where you left of. You simply browse to the main page of the blog and click "Domain: Back" and it should take you to the last page you where reading on this specific domain.
Select "Domain: Back" and "Domain: Forward" from the menu or use the keyboard shortcuts Shift+Alt+LeftArrow and Shift+Alt+RightArrow.