Lightning is Bitcoin's second layer for instant payments: channels between parties hold funds and settle balances off-chain, with the Bitcoin ledger as judge only when a channel closes. Payments route across channels in milliseconds for fees near zero.
The trade is capacity for complexity: Lightning excels at small, fast payments and demands liquidity management that on-chain settlement does not. For coffee it is unbeatable; for payroll, on-chain still wins.
Lightning is a first-class rail on U.CASH checkouts: instant Bitcoin beside the bank rails and the cards, settled on-chain, non-custodial.
Every term behind the rails, the assets, and the settlement.