The era of decentralized finance (DeFi) has ushered in never-before-seen revolutions in the way people deal with money, assets, and investments. The cornerstone of this revolution is the stablecoin concept, and among stablecoins, fiat-collateralized stablecoins are one of the most reliable ones. Why did fiat-collateralized stablecoins become so crucial, and why are they the backbone of DeFi Lending and Borrowing? To effectively tackle this, it is essential to know what they are, how they operate, and the important place they hold in the broader digital finance landscape.