Medicine doctors provide medical care to a variety of patients, ranging from infants to the elderly. They can treat patients at their own homes, in hospitals or at assisted-living facilities. Some work in emergency rooms, while others provide care to whole families. Some specialize in different areas of medicine, such as the digestive system. They can help patients with problems such as ulcers, jaundice, diarrhea, and abdominal pain. Some are even trained to perform procedures like colonoscopies. Regardless of specialization, medicine doctors are required to have broad knowledge of the medical system. This means understanding the larger context of health care and knowing where to find resources to help patients. There are two main types of medical doctors: MDs and DOs. Both specialize in a different area, but both have similar educational backgrounds and are licensed to practice in every state. Internal medicine doctors specialize in diseases affecting the internal systems of the body. Their practice focuses on diagnosis, treatment, and prevention. They treat a wide range of illnesses and conditions, such as heart disease, lung disease, and digestive disorders. They emphasize whole-person care and are skilled at managing complex conditions. They typically train in hospitals or outpatient centers for three years. They also undergo additional training in specific fields, such as neurology or obstetrics. During their third year of medical school, students must take the United States Medical Licensing Examination (USMLE) to become licensed to practice medicine. The exam tests students' knowledge of clinical science, and core scientific principles. Clinical rotations also help students apply what they've learned in the classroom in real-world situations.