Critical Appraisal is the process of ensuring the research you've discovered meets a baseline of reliability. According to LoBiondo-Wood & Haber (2017):
The critical appraisal of research studies is an organized, systematic approach to evaluating a research study...using a set of standardized critical appraisal criteria. The criteria are used to objectively determine the strength, quality, quantity, and consistency of evidence provided by the available literature to determine its applicability to practice, policy, and education.
Functionally, this means not taking every article you find at face value. Sadly, there are bad actors in the world of scholarly publishing who promote poor research for personal gain, and your responsibility as a practitioner of EBP is to be well-informed and scrupulous: a true master of information literacy.
Fortunately, there are numerous resources and guides to appraise an article. This is a major endeavor, and as you might imagine, different study types and questions require different forms of appraisal. The links below should get you started, but if you ever have a question about the validity of a source, don't hesitate to contact your librarian!