The sticker links every participating Story into a browsable collection around one prompt. Because each addition is visible to that person's followers with a tappable sticker to join, the chain can spread rapidly, pulling in new participants the way a hashtag challenge does.
For creators and brands it is a low-effort engagement and reach tool: start a relevant prompt, and participation both boosts your Story's visibility and seeds a trend you originated. It works best with prompts that are easy to answer and broadly relatable.
