Give credit where credit is due; cite your sources.
Citing or documenting the sources used in your research serves two purposes, it gives proper credit to the authors of the materials used, and it allows those who are reading your work to duplicate your research and locate the sources that you have listed as references. When other authors cite their sources properly, you can also use their research to help you with your own!
Knowingly representing the work of others as your own is plagiarism. Use the "plagiarism" tab in this guide to help you properly cite and avoid plagiarizing another persons work.