Citing your sources properly -- yes, even the charts and graphs you reuse from other sources, and the statistics you quote -- is important and required.
Purdue University's OWL Writing Lab Citation resources are the best ones out there on the web. Generally, Business & Economics courses require that you use APA citation style. Detailed information both in-text references and "works cited" pages is available here.
Diane can help with citations, too!
Reference books like dictionaries and encyclopedias can provide essential background knowlege for any topic you are investigating, and provide you with pecise definitions of difficult terms. While the free web provides many resources, the information you may find there isn't always reliable -- Wikipedia, for example, is still not a resource for serious academic research because it is so changeable and authorship is not verifiable.
Here are links for two useful online resources for background information and important definitions -- but don't neglect the important print resources we have available in Myrin. Specialized encyclopedias and dictionaries provide quick reference and can be invaluable in solidifying your understanding of a topic as you begin your research into the more complex realm of statistics, academic journal articles, and books.