Some human foods can be very dangerous to dogs and as a general rule it is best to just give them dog food and dog treats only.

Giving dogs left overs is also a bad idea as they could contain an ingredient which can disagree with them or even do them harm.
Human food, as treats or left overs, can give your dog more energy that it needs resulting in weight gain.

Some foods are OK such as raw carrots, just make sure you never give your dog any of the foods listed below as these can harm your dog.