Dictatorship:
one person (or a small groups of people) have all the power in the country and they keep this power by fear. For example, right now in North Korea many people and their families are dying if they don't agree with the regime
Democracy:
the leader does not have full control over the people and can be removed if the people don't agree with how the leader, or at least not get elected again. For example, right now in Brazil people are dissatisfied with the government of Dilma Rousseff so they likely won't elect her again.