Herding is a skill used to provide increased control over tamed pets. It is not a requirement for being a tamer, but it does provide several benefits. It is used to increase movement speed of your pets and to provide a targeted damage buff for them by way of Herding's skill ability Aggression.
A herder can direct his follower's aggression at single target providing a melee damage boost for followers.
Stacking Additional uses of Aggression will cause the effect modifier to increase up to 3 stacks and renew its duration.
To gain skill in Herding, you need only use Aggression on a target and have your creatures attack it. The follower's owner will have a chance to gain skill in Herding when followers attacking this target.