The precise nutritional choices before, during and after a workout depend upon what activity you did, for you long and at what intensity. It can also depend on what your goals are!
To keep this simple, refueling after a workout is a smart idea. It is the best time to eat any starchy carbohydrates because your glycogen stores have been reduced (glycogen is a major fuel source during a workout). Having a green smoothie with protein is a great option or a sweet potato and a protein choice.