There are many reasons why it is important to cite the resources that you consult when doing research. The most important of these are:
What is plagiarism?
Plagiarism is using another person's work without giving them credit.
At UVM plagiarizing, whether intentional or by accident, is a violation of the Code of Academic Integrity (PDF).
Easy ways to avoid plagiarizing:
There are several major citation styles. Which one you should use depends upon the subject area of the class and the preferences of your professor.