Where Do They Grow?
I don't think that I responded in time, but in nature, grapes grow in the understory of a forest and then climb up trees to get to the light at the top of trees.
In a commercial farm, they would grow out in the open on a trellis, so that a grower can control how much light, fertilizer, and water they receive to get the best fruit quality. Since they are vines, they still need something to cling to, and that's why we use a trellis.
I hope that helped you understand where grapes grow!