“Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients" (Sackett et al., 1996, p. 71). Also called evidence-based practice, EBM incorporates the practitioner's expertise and clinical judgement with relevant scientific evidence to honor patients' values and preferences in recommending treatment.
Reference
Sackett, D. L., Rosenberg, W. M., Gray, J. A., Haynes, R. B., & Richardson, W. S. (1996). Evidence based medicine: what it is and what it isn't. BMJ (Clinical research ed.), 312(7023), 71–72. https://doi.org/10.1136/bmj.312.7023.71, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2349778/
Dartmouth's Evidence Pyramid provides a way to visualize both the quality of evidence and the amount of evidence available. For example, systematic reviews are at the top of the pyramid, meaning they are both the highest level of evidence and the least common. As you go down the pyramid, the amount of evidence will increase as the quality of the evidence decreases. Image credit: EBM Pyramid by Trustees of Dartmouth College and Yale University.
Here's another take on the evidence pyramid indicating primary vs. secondary sources and explaining each level.