Off-chain refers to transactions or activities that occur outside the blockchain network. These transactions are processed without being recorded on the blockchain, often resulting in faster and more cost-effective transactions. Off-chain solutions are used to reduce the burden on a blockchain, improve scalability, and manage costs, especially for small or frequent transactions. Common off-chain methods include state channels, sidechains, and off-chain computation. However, as these transactions occur outside the blockchain, they rely on different security mechanisms and may sacrifice some degree of decentralization and trustlessness inherent in on-chain transactions.