Fully backed and over collateralized — Every stablecoin issued is backed by reserve assets in a vault that represents more than 100% of the total Stablecoins issued.
The total market cap of all stablecoins is close to $200B. This represents around 10% of the entire crypto industry. They have quickly become a critically important piece of most DeFi products. There are several ways to create a dollar-pegged token, and each strategy comes with some tradeoffs.
Hybrid — Some projects like Frax Finance use a hybrid approach to find a balance between these issues. The peg to USD is algorithmically maintained, but they also have reserves available to handle periods of extreme volatility and market demand. This strategy seems the most likely to survive long term.
Algorithmic — The value and supply of algorithmic stablecoins are controlled by code. If the demand for the coin starts to increase rapidly, the protocol automatically creates more coins to bring the price down. If the value drops too low, some of the supply is burned to bring the price back up.