In order to search the literature effectively, you must construct a searchable question. This will not necessarily be the same as your research question. You may need to formulate multiple searchable questions in order to provide the necessary background for clinical research or a structured literature review. A clinical research question tests a hypothesis. A literature search question:
Literature search questions can be structured in many ways depending upon the type of question and what the searcher hopes to identify in the existing literature.
In a nutshell, primary sources are original works, secondary sources synthesize or utilize primary sources.