When physicians want to make a decision based on evidence they ask a question. For instance, how effective and safe a given drug is to treat a disease.
To answer it, they need to carry out an exhaustive search through databases for research studies (observational studies, randomized studies, systematic reviews with meta-analyses, network meta-analyses).
Then, they need to process that information, appraise the trustworthiness of it and finally be able to make a recommendation that will guide their practice. This task is very complex and usually time-consuming.