The USMLE is a three steps examination and the various steps evaluates the candidates in different areas:

USMLE Step 1: 
Assesses whether medical school students or graduates understand and can apply important concepts of the Basic sciences to the practice of medicine. 

USMLE Step 2: 
Assesses whether medical school students or graduates can apply medical knowledge, skills and understanding of clinical science for providing safe patient care under supervision. 

USMLE Step 3: 
Assesses whether medical school graduates can apply medical knowledge and understanding of biomedical and clinical science essential for the unsupervised practice of medicine. 

As the examinee goes through the various steps of the examination, their ability to apply their knowledge, concepts and principles in relation to patient care are assessed. The examination should be completed within a seven-year period in order to obtain a medical license, and not more than 6 attempts to pass each step are allowed.