why dogs behave the way they do

Your dog adores you and wants to please you. But Rover finds the training process perplexing because you are asking him to do things that he would never be required to do in the wild.  For example: 

DOGS NEVER WALK IN A STRAIGHT LINE

Dogs have evolved to process their world through smell, and when they walk their bodies  follow their noses. They possess up to 300 million scent receptors in their noses, compared to about six million in us. Is it any wonder that they want to smell everything on a walk? 

Dogs bark to communicate, so they are baffled when you yell at them to be quiet. This is especially true for certain working breeds who think they are helpfully warning you of a possible danger.  Dogs also bark because they are bored.