2 Cons Equal 1 Pro
It takes both CONsequences and CONsistency in order to get PROficient training with dogs. That's how they learn best. But what is learning? It involves some sort of the change in behavior that lasts awhile. Whatever causes a change in behavior must have something to do with past experience. Animals learn these relationships the same as do people.
Basically, the "Law of Effect" states that if a consequence of a behavior is pleasant, the preceding behavior becomes more likely to occur again. If a consequence is unpleasant, the preceding behavior becomes less likely to occur again.
There are 4 possible scenarios in which we can provide consequences to our pups in order to increase or decrease the likelihood of a particular behavior occurring again in the future, two of which increase the likelihood (reinforcement) and the other two of which decrease the likelihood (punishment).
Positive Reinforcement - presentation of a good consequence (like a food treat) when the dog's response is performed, so as to increase the likelihood of the response in the
Negative Reinforcement - removal of a bad consequence (like when you stop choking your dog with a noose collar) when the response is performed, so as to increase the likelihood of the response in the future.
Positive Punishment - the presentation of a bad consequence when the response is performed (like after asking your dog to sit he lays down and you present him with a jerk on his leash to sit up). Ultimately, this leads to a decrease in the likelihood of the response in the future.
Negative Punishment - the removal of a good consequence when the response is performed (like after asking the dog to sit he lays down, and you eat the treat you were just about to give him). Ultimately, this leads to a decrease in the likelihood of the response in the future.
Make sure you know whether or not you're trying to increase or decrease the likelihood of a behavior/response before attempting to train your dog one-way-or-the another. Then, choose the appropriate method from above to encourage or discourage the behavioral response. Please keep in mind that you want to use the most humane way of getting your point across to your pup do be careful and thoughtful when providing punishments.