You'll read through a lot of sources of information to thoroughly understand your topic. Once you've done so, you'll need to evaluate them to determine which ones will go in your literature review.
Should you consider using that resource or is it crappy? The CRAAP test gives you a set of guidelines to consider when evaluating a source of information. Remember, this isn't a checklist, but you should carefully consider each item.
Consider these questions when looking at bibliographic citations that authors cite in their research. You may not want to chase down every one of them. This will save you time.