Its just great to be greeted with a high-quality photo whenever you start your browser or open a new tab. They have a good resolution with a description and a link to the photographer so you can easily download one as a wallpaper. There are various other options you can add. Out of the box you get what you see on the website but with a name (and title!) of your choosing, and a bunch more if you make an account or even plus account. Thankfully, if you decide to go without one then this add-on will not keep bothering you about it.