Answer: The republics are usually presidential or parliamentary. In the former it is the people who elect the president or head of state and in the latter it is the parliament who elects it. in some and in others the powers of the president are different. Examples of the first are in the US or in some republics of south america and the latter are found in Europe in countries such as Germany or Italy.
Democracy is about a mode of election of the rulers of a certain state. We have two modes of democratic exercise: direct or by representation.