eCash is a custodial but very private way to send a “bearer instrument” (like cash) back and forth, but (unlike wallet of satoshi) the custodian doesn’t really much about who transacts with who, or for how much, thanks to the cryptography involved.

With Cashu, it’s an eCash protocol, but instead of representing dollars (which is why the first eCash experiments failed), a Cashu token’s value is pegged to Bitcoin, and the custodian (“mint”) presumably hold exactly the right amount of Bitcoin in relation to the value of the Cashu notes they have issued.

Happy to answer questions if unclear; I’m still learning this myself 🤙