There are different scurry's but the main aim is for your dog to retrieve a dummy, its timed and the fastest time wins
Different scurry's would be:
Obsticle, where your dog goes out jumping over obsticles such as straw bales, retrieves the dummy and runs back jumping over the obsticles on the return. Quite simple but speed is the essence.
Then you have (not sure what its called) a scurry where 1 dummy is fired out in a field in some rough cover, your dog has to retrieve and get it back to you, then it has to go out for a second retrieve which will be in a different place, again its all about time.
Rabbit distraction (which is my Belle's speciality)
The dummy is fired out, the dog is set out to retrieve but as they get out half way a rabbit dummy is quickly released right at the foot of the dog whilst they are in full speed, the aim is for your dog to ignore the rabbit and continue with the 1st retrieve again its about time, this scurry is one of the hardest as your dog has to be 100% steady to distraction and chasing.
There is probaby more which involve other obsticles but most are about speed retrieving