sfrxETH is a ERC-4626 vault designed to accrue the staking yield of the Frax ETH validators. At any time, frxETH can be exchanged for sfrxETH by depositing it into the sfrxETH vault, which allows users to earn staking yield on their frxETH. Over time, as validators accrue staking yield, an equivalent amount of frxETH is minted and added to the vault, allowing users to redeem their sfrxETH for an greater amount of frxETH than they deposited.
The exchange rate of frxETH per sfrxETH increases over time as staking rewards are added to the vault. By holding sfrxETH you hold a % claim on an increasing amount of the vault's frxETH, splitting staking rewards up among sfrxETH holders proportional to their share of the total sfrxETH. This is similar to other autocompounding tokens like Aave's aUSDC and Compound's cUSDC.
Frax Finance is a fractional stablecoin protocol. Frax is open-source, permissionless, and entirely on-chain – currently implemented on Ethereum and 12 other chains. The end goal of the Frax protocol is to provide a highly scalable, decentralized, algorithmic money in place of fixed-supply digital assets like BTC.
The Frax ecosystem has 2 stablecoins: FRAX (pegged to the US dollar) & FPI (pegged to the US Consumer Price Index). The Frax Finance economy is composed primarily of the two stablecoins, a native AMM (Fraxswap), and a lending facility (Fraxlend).