In the context of cryptocurrency, Lightning refers to the Lightning Network, a second-layer solution designed to enable fast and low-cost transactions on top of a blockchain like Bitcoin. The Lightning Network seeks to alleviate scalability issues inherent to many traditional blockchains, which can only process a limited number of transactions per second (TPS). Instead of recording every microtransaction on the main blockchain, the Lightning Network creates off-chain payment channels between parties, allowing them to transact almost instantly with minimal fees. Only when the payment channel is closed or a settlement is required do the transactions get recorded on the main blockchain. This innovation aims to make cryptocurrencies more practical for everyday use, including micropayments and high-frequency transactions, without sacrificing the decentralized ethos of blockchain technology.