College research assignments ask you to pose a question worth exploring, to read widely in search of possible answers, to interpret what you read, to draw reasoned conclusions, and to support those conclusions with valid and well-documented evidence.
Well-documented evidence typically relies on citing source material. In researched writing, sources are cited for several reasons:
It is important to acknowledge the contributions of others. If you fail to credit sources properly, you commit plagiarism, a serious academic offense.
Choosing good sources will add credibility to your work; in a sense, you are calling on authorities to serve as expert witnesses. The more care you have taken in choosing reliable sources, the stronger your argument will be.
Most importantly—you are helping to build knowledge by showing readers where they can pursue your topic in greater depth.