Citation searching is a strategy for collecting relevant sources on your topic.
Say you have found an important, scholarly article on your topic. Before she wrote the article, the author went through a research process that was likely very similar to the one you are going through right now. She found a number of good articles on her topic, and then she created a References list. That References list is like a trail of breadcrumbs that you can follow back to more important, scholarly articles on your topic.
Always look at the References list at the end of each article you find, to see if any of the listed sources might be useful!