"Off-chain" refers to any data or transactions that occur outside of a blockchain network. This means that the information is not recorded directly on the blockchain, which can help reduce congestion and improve transaction speeds. Off-chain solutions are often used to handle large volumes of transactions or to store data that doesn't need the security of a blockchain. Examples of off-chain methods include traditional databases, payment channels, and sidechains. These approaches allow for greater flexibility and efficiency while still enabling users to interact with the main blockchain, such as Bitcoin or Ethereum, when necessary.