Some students have a background, identity, interest, or talent that is so meaningful they believe their application would be incomplete without it. The prompt gives you a lot of latitude for answering the question since you can write a story about your "background, identity, interest, or talent." Your "background" can be a broad environmental factor that contributed to your development such as growing up in a military family, living in an interesting place, or dealing with an unusual family situation.
If this sounds like you, then please share your story. You could write about an event or series of events that had a profound impact on your identity.
The answer to the final question about the "outcome" of your challenge need not be a success story.
Sometimes in retrospection, we discover that the cost of an action was perhaps too great.
For the 2019-20 application cycle, the Common Application essay prompts remain unchanged from the 2018-19 cycle.
With the inclusion of the popular "Topic of Your Choice" option, you have the opportunity to write about anything you want to share with the folks in the admissions office.
Describe a problem you've solved or a problem you'd like to solve.
It can be an intellectual challenge, a research query, an ethical dilemma--anything that is of personal importance, no matter the scale.
Recount a time when you faced a challenge, setback, or failure.
How did it affect you, and what did you learn from the experience?