Citing sources is interacting with sources.

It's important that you include the thoughts of established experts to support arguments or ideas that you're presenting in your work. It's also important that you include your own thoughts and ideas when discussing what experts are saying. 

Watch these two videos to understand what citation is, and how to interact with academic sources such as books and articles.

When you interact with sources, you need to do two things:

1. Tell your professor whether a thought in your paper is your thought of the thought of someone else
2. Tell your professor where to find that thought, if it was the thought of someone else

Essentially, your professors want to know what parts of your paper or project are your original thoughts and what parts are someone else's thoughts. If they are someone else's thoughts, your professors want to know where you found them (ie. in a book, article, or other resource).

Watch these two videos to understand how to cite thoroughly and how to avoid accidental plagiarism.

The Citation Guide provides details and links to information to help you find all the guidance you need to write in-text citations and format your references sections.