Reactivity: Dogs who bark, lunge or growl at other people, dogs or moving vehicles while on or off leash, with no intention to injure.

Leash Reactivity: When a dog barks, lunges, or growls while on a leash, typically as they are trying to get to a dog person or a moving vehicle

Aggression: Dogs who bark, lunge or growl at other people, dogs, or moving vehicles while on or off-leash. (They have an intention to injury and likely have bitten or been involved in dog fights in the past)

Defensive Aggression: If your dog is forced to be in an uncomfortable situation and react aggressively to protect itself around another dog or person.  Usually, in these cases, these bites are small warnings snaps. and don't leave much damage. 

Offensive Aggression: If your dog has options but chooses to put themself in a situation where they bully or act aggressively towards a person or dog, they have offensive aggression.  Usually, these bites are more serious and sometimes need stitches. 

Doggy Daycare Syndrome: Dogs who go to doggy daycare often who then bark, and lunge at other dogs when on a leash but can be fine with other dogs while off-leash.  These dogs are reactive and frustrated.