Fortunes are an optional component that add some randomness and excitement to exploration scenarios. Represented through either a deck of cards or a table, Fortunes provide random rewards (and occasionally penalties) from Searching a region. When you find a Fortune through a Search, either draw a Fortune card (if using decks) or roll 1d100 (if using the table) to see what you've found. Fortunes commonly result in acquisition of Valuables.
For more information, see Player's Guide Chapter 5: Exploration.