Citing your sources is an important part of the writing process. Documenting your sources gives credit to authors whose thoughts and ideas you have incorporated into your work. Proper citation helps you as a writer by strengthening your position and showing the depth of your research. Citing also helps your readers verify what you've written and follow up with sources they find interesting.
Most importantly, proper citation will help you avoid plagiarism.
How can I effectively cite the sources I use?
Proper citation will link text and facts used in your papers and presentations to the relevant sources quoted or consulted. APA is the most common citation format for the social sciences.