Dogs (and humans) need protein, carbohydrates, fat, vitamins, and minerals. Too much or too little of any may cause problems such as obesity, malnourishment, or even vitamin or mineral toxicity. But don't panic! After all, you have been feeding yourself for many years without much thought.
Dogs have many of the same requirements as people do, but may be more flexible in their ability to deal with some imbalances. It is important, however, that you have an understanding of where your needs differ from those of your animal friend.