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.
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: