Summary is the most general type of reference and is used when you condense an extended idea or argument. It should be done in your own words and should not follow the sentence structure of the original. Quotation is used to indicate that the words you are using are not your own. All passages taken directly from a source should be enclosed in quotation marks and should be double-checked for accuracy. This means that you must set up the quote properly.
Environmental issues are important in the study of cancer research.
Although many studies have suggested that DNA will be help scientists find a cure for cancer, Richard Lathke, director of the Center for the Study of Immune Disorders at the University of Michigan, believes that environmental issues should take precedence in current research. In the first example, the writer gives no indication of who is speaking, or why their words are important. The words just appear, in a single sentence that is plunked into the middle of the argument. The second example explains where the quote comes from and also incorporates it into a grammatically correct sentence.