It’s an implementation of chaumian ecash. No blockchain, basically you can deposit bitcoin(over lightning) into a mint which will issue you a claim to that amount of sats which you can send to others asp using that mint (centralized) or make payments out to others accepting lightning which will burn your ecash and send sats over lightning. It’s trusted and centralized like wallet of satoshi however the balances and payments are hidden from the mint due to blinded signatures