The MongoDB World 2019 JAM Session Challenge required participants to create a web application with Stitch's QueryAnywhere, using a specific database access rule, and then deploy the application online with Stitch Hosting. The challenge involved creating a query object from user selections, sending it to the database, and performing an aggregation pipeline to calculate average prices and counts of matching properties. The solution also included refreshing a table with the aggregated data and updating a UI element with the results.