The Community Chest is (free) additional game content. These items, weapons, and armor will be available for your Hero to buy from Merchants in-game.
The additional Classes & Races will be available to be picked and played at Character Creation.
Example: You've given us a concept for a Potion Item that you really like. We balance, format, and put it into the Community Chest. Now when you play the game, that item will be added to list of available goods merchants can sell.
Example 2: You really want to play as a Warlock, but don't see that class as an option. You Pledge to become an Acolyte so you can make one. After giving us a concept about this class, we'll implement it into the Community Chest for you to choose at Character Creation.