"From my understanding, the key helps uniquely tag and identify elements as we iterate through them in the JSX. For example, I'm iterating through each elements of this array and displaying them in the tag, so I need to have a key tied to each element. I could use the arrays index number as the key for each element." The interviewer then asked, what else could we use from the data set. So I went back and had a look at the data set and saw that each object had a unique ID so chose this.