Principal Token (PT): Represents the underlying asset, and after expiration, PT can be redeemed for the underlying asset at a one-to-one ratio. For example, 1 PT-stETH can be redeemed for 1 ETH worth of stETH.
Yield token (YT): Enables investors to receive the yields generated by the underlying asset. For instance, holding 10 YT-stETH allows investors to receive all the yields from the 10 ETH deposited in Lido.