Looking at Ankr DeFi (opens in a new tab), you can see the Difference vs. Fair value column.
Fair Value represents the ratio at which users can stake/unstake 1 token. The Fair Value of reward-bearing tokens, such as ankrETH, is always higher than 1. This is because staking rewards accumulate and can be realized when users unstake. Fair Value of ankrETH therefore continuously increases as the ETH staking rewards accumulate.
The ankrETH redemption price is also applied when staking ETH to avoid existing stakers being diluted by new stakers. In other words, if the redemption price of 1 ankrETH is 1.05 ETH, a new user willing to stake ETH will get 1/1.05 = 0.9524 ankrETH for staking 1 ETH.
Along with the trading options, you can see the Ankr Staking row with a Stake or Unstake button depending on the source asset you choose.
Ankr DeFi Trade will compare prices on the market with Ankr's Fair Value to indicate whether it is more attractive to stake, or trade. This tool was created to help stakers make better-informed decisions.