This is a collective motion simulation based on the so-called Vicsek model (Wikipedia article). The particles represent for example fish, locusts, or birds. They move with fixed velocity (self-propelled) and adjust their movement direction to their neighbours. This is similar to a ferromagnet where microscopic magnets adjust their spins but don't change position. As the magnet, the moving system can show a "phase transition" from unordered to swarm-like, depending on the strength of the random perturbations. Interestingly a similar effect of organized motion can be observed if particles repel each other (Grossman, Aranson and Jacob 2008)