Pediatric Doctor(pediatrician) vs. ER doctor?

Pediatrics (general) treats the range of kids' ailments, as well as health maintenance for kids who aren't ill at all. Emergency medicine is exactly that, though most people in the emergency department don't have major emergencies. Of course, just to make sure you're really befuddled, there's also pediatric emergency medicine, a popular specialty. At any rate, if you were far enough along in medical school to be worrying about the differences, then you wouldn't have to ask. There's no hurry.