Research, like writing, is recursive. We go back to what we know in order to figure out where we might want to go next. We keep circling back in order to go forward. It's an ever-looping spiral with your research question at the center.
You find sources. You take notes. You learn new subtopics, new perspectives, you find new angles. You take this information to a new search for new sources. You take more notes. You think about this new information and begin to develop an organization in your head. You develop more questions, so you find more sources...