Give credit where credit is due. By properly citing the sources you use in your research projects you are both identifying the resources that you used to complete your work and you are formally acknowledging the authors or creators of those resources.
Citation Management tools are web-based programs that allow you to easily collect, manage, and organize bibliographic references by interfacing with databases. They can also interface directly with Word, making it easy to import references and incorporate them into your writing, properly formatted according to the style of your choice. For more information see Cornell Library's Citation Management page.
You'll find many references in the course of your research. Make sure you keep track of what you find! The library offers some great tools to help.