Swarm shows you what websites people are visiting, right now.
Swarm is a graphical map of hundreds of websites, all connecting to each other. It updates itself every second with where people are going and coming from. As sites become more popular, they move towards the center of the swarm and grow larger. Conversely, sites that lose traffic move away from the center and grow smaller.
Website traffic is symbolized with thin lines. Each time you see a line appear, it means someone has moved from one site to the other. You can gauge how many people are swarming around based on the number of lines.