Unlike regular web searching, academic research is typically done within the intellectual confines of a specific discipline, such as history, rhetoric, political science, physics or public health. Annoying? Here's why
Scholars in a particular discipline share common understandings of what kinds of problems to research, what analytical methodologies to use, what kinds of evidence are valid-- even what kinds of questions to ask. They usually want to read what other scholars in their discipline are saying, and not sort through material from other disciplines.
You, the student, need to know what discipline/s you should use to research a problem, in order to find the right kinds of sources.