Final answer:
Signal phrases are used to call attention to an internal citation of quoted or paraphrased information from another source.
Step-by-step explanation:
Signal phrases are used to call attention to an internal citation of quoted or paraphrased information from another source. They are important because they provide context and indicate that the words or ideas that follow are not the author's original work. Signal phrases can vary in placement and wording to avoid monotony and add variety to writing.