Lightning - Bitcoin is first locked into a payment channel on the main Bitcoin blockchain. Once the channel is open, users can conduct an unlimited number of transactions off-chain within that channel. Cashu - Utility tokens that are redeemable for Bitcoin. They are an IOU or digital cash equivalent secured by a trusted (or federated) mint, which is a key difference from holding the Bitcoin itself in your non-custodial wallet. This introduces an element of custody and trust in the mint operator that is not present in running a node.