"Dog Agility is a fun sport for both dogs and their people. It accentuates teamwork whereby the handler directs and guides the dog through, under and over various obstacles starting at beginner level on leash.
Agility exercises also gives the dog a better sense of balance, improves co-ordination and requires more focus, concentration and problem solving abilities. Once you and your dog have completed basic obedience training, agility is a fun way to continue your training to a higher level, building and working toward off leash control. Agility is an excellent way to continue working with your dog in a safe environment, giving your dog a job to do and thereby stimulating its brain."
The following sequence is a good way to demonstrate what Nina says above. The dog needs to weed through an obstacle course on direction of the handler. Nina's dog Daisy is advanced and can complete this exercise without leash.