The concept of Stem farm is the same as Yield Farming in Decentralized Finance that requires the pair of 2 tokens to be added in the liquidity pool, BUT in Morning Moon Village, most of the contracts of the farmland are consist of the pair of LUMI, which is the governance token of this game, and other coin that player select to staking.
Therefore, the player only need to trade only one type of Token in the shop and the game system will automatically convert the token into pair of LP Token ready to farm. That is called Stem.