The U.S. Medical Licensing Examination (USMLE) Step 2 Clinical Knowledge (CK) exam tests a physician's ability to apply medical knowledge and skills to patient care, focusing on health promotion and disease prevention. It's a one-day exam with 318 questions spread across eight 60-minute blocks within a 9-hour session. The exam covers topics like Internal Medicine, Obstetrics and Gynecology, Pediatrics, and Surgery, with a focus on applying clinical science principles for safe patient care.