Poaching, in general, is considered to be a healthier way to prepare food because you aren't using any fats or oils, but water to cook. When you do poach you are using hot water that is simmering, not boiling. And when you are poaching an egg, this is vital because you don't want your egg to fall apart! Adding vinegar to the poaching water helps the egg whites firm faster and prevents them from spreading out loose and free in the water.