Critical appraisal is the process of carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value and relevance in a particular context. Critical appraisal looks at the way a study is conducted and examines factors such as internal validity, generalizability and relevance.
This is especially true of information found on the open web, via Google or other search engines. While there is high-quality information to be found, there is also utter crap. Whether for one of your courses or for your personal use, one of the key parts of the research process is evaluating your information, i.e., using your Crap Detector.