The Bountiful mod brings to the game a new block called the Bounty Board. These boards will generate in villages and if you right click it, it will bring up the bounties. These bounties often ask for you to bring back an item, or kill some mobs in return for whatever rewards they’re offering. To redeem these rewards, right click the board with the bounty and you will receive the reward.
This mod also adds another item called a Decree. A Decree determines what kind of bounties show up on a bounty board. For example, an Armorsmithing Decree makes it so that objectives and rewards related to armor show up on the board (leather, iron, chestplates, boots, etc). Up to three decrees are allowed on a bounty board at once, and it will mix and match objectives and rewards from all three when new bounties appear!
You can find new Decrees as rewards for certain bounties, or they can be traded with villagers at higher villager levels.
Just like items, bounties can have different tiers of rarity. Some bounty rewards are more rare than others, and bounties with higher rarity have a better chance of having these more rare rewards! Rarity follows the same pattern as in vanilla: Common, Uncommon, Rare and Epic.
Note: Bountiful requires Kottle.