Arc gets it’s name from lines that link related stories in the outer ring across topics. Stories are linked when an user diggs 2 or more different stories. This makes for a more effective way to discover new topics and stories.
To finish off, Arc has a full screen view that makes use of your whole screen. Nice feature. Now you can see how information grows. Literally.
I like the idea behind the tool very much. It’s a new way to present and discover information.
Source: Digg Labs