Understanding your dog...
Pack drive - the desire to be with the master of family.
Prey drive - instinctive desire to chase anything that moves. This includes more than just living animals; things such as toys, balls, frisbees, etc. and is a dog trainer's best friend.
Active aggression - directly related to prey. It's seen in dogs with extreme prey drive. This is when a dog actively demands it's prey either when it can't get to the prey or when the prey is not moving. Barking will usually go into a high pitch or scream in order to panic the prey into moving so the dog can seize it.
Defensive aggression - reactive aggression due to a threat related to self-preservation directly related to flight instinct.
Social aggression - the desire to establish pack dominance. This is a very dangerous true form of aggression in that it is not related to flight instinct. This is a dog that will challenge most people that it comes in contact with. It is not limited to the owner if pack dominance has not yet been established. This is a problem that should be rectified immediately.
Environmental Aggression - also known as "territorial" aggression. It is another dangerous and true form of aggression where the dog guards objects and areas it perceives as it's own. If not addressed immediately, the dog may slowly start to take over the home.
Flight Instinct - Instinctive response to a perceived threat in which the dog feels it must flee to preserve it's safety. Dogs that have high levels of flight are considered to have weak nerves and will generally have fears of loud noises, new environments, people, etc. This is an instinct that must be blocked, and the dog must be trained to understand that flight is negative and coming through it's fear is positive.