Challenges are themed storytelling contests that Vocal creators can enter to win cash prizes.
All Challenges have different prompts related to all sorts of themes, and all run for differing amounts of time. Some Challenges are open to all creators; some Challenges are exclusively open to Vocal+ members. In addition to longer Challenges, which have running times between one and two months, Vocal+ members also have exclusive access to Weekly Challenges, meaning a new prompt and a new chance to win a cash prize every single week.
You can see all Challenges on Vocal here, and click into any of them to learn more about each particular Challenge.