Getting background information and general facts about your topic is a good way to start your research. This not only helps you better understand your topic, but it also helps you formulate the boundaries of your research and key terms for your thesis statement. It can be a helpful guide to begin to narrow down your topic into a coherent and specific area.
The Concise Oxford Dictionary of Politics and International Relations by "Grey literature" refers to stuff that is rigorous and well-researched, but doesn't neatly fit into the major categories of peer-reviewed articles and scholarly books.
Examples of grey literature:
Whether or not grey literature will be useful and appropriate depends on your information need and where the information is coming from.