The Question is,
"Tell us about how you might like to make a positive impact in the world through your studies at ***University."
so should I focus on what will be the impact? Or it's only a study-plan kind of essay?
The way I read it, it is asking how you will use your education to make the world a better place. Will you study medicine and ease the suffering of millions? Will you study architecture and build beautiful and safe buildings? Will you become a teacher and share your passion of history with your students?
Describe a plan for action. Tell them what you will do in the next five years, in the next ten years. If you had a clear plan for the future, this would be an easy essay to write. First look to your future; then start typing the essay. If you don't know what your major/career is going to be, think of one tentatively, and imaginatively come up with a tentative plan for the future.
Well, thanks for the idea :)