"Deductive reasoning is a logical process in which a conclusion is based on the concordance of multiple premises that are generally assumed to be true. "
What the statement above means that you use one reason to kind of prove another reason. For example:
All people are human.
Elizabeth is a person.
Elizabeth is human.
Because I said that all people are human, and Elizabeth is a person, then, she is a human.
I really hope that this helps.. If not ,have mercy ,this is my second question.xD