Bungeoppang sold by street food stalls are made on a large waffle-iron like appliance. The ones I've seen are typically round with six or eight fish-shaped molds. First, a batter of wheat flour, baking powder, water and/or milk and sometimes eggs is added to each mold. Then the filling is added to the middle of the fish shape. Usually they make the fillings ahead of time in large batches. They then pour a little more batter to cover the filling and shut the mold. After a couple minutes, they open the mold and pop out the hot and crispy bungeoppang. The batter is similar to a waffle but softer. Smaller molds are available online to make bungeoppang at home, and I definitely will be getting one when I return to the US!
Yes, it is definitely connected to the local environment. Like many busy, crowded cities, walking is the main mode of transportation for most people around their local area. Street food is great for busy people to eat on the run. Especially in the winter, walking out in the cold for long periods of time can really wear you down. Having a break with a quick hot snack is perfect for getting a little more warmth and energy to continue on.