According to @0xMoon6626, USDD is a decentralized stablecoin issued by the TRON DAO Reserve, designed to maintain a 1:1 peg with the US dollar through an algorithm and over-collateralization. The guide details how traders can acquire USDD and where to purchase it, emphasizing its key advantage of offering a 20% APY opportunity. This information is crucial for traders looking to capitalize on stable and high returns in the cryptocurrency market.