Successful research papers cite a variety of sources. The following videos describe the most common types you'll encounter online and in the library.
Primary and Secondary Sources (1:43)
Popular and Scholarly Sources (2:55)
If you're new to scholarly sources, they can be challenging to read and understand at first. They're typically written by researchers for researchers (this includes your professors). Give yourself plenty of time and ask for help if there's something you don't understand. Here are a couple of related videos: