"On-chain" refers to any action or transaction that occurs on the blockchain and is recorded on the blockchain ledger. This includes transactions of blockchain digital assets, smart contract executions, and data storage. On-chain transactions are public, transparent, and immutable, meaning that once recorded, they cannot be altered or deleted.
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"Off-chain," on the other hand, refers to any action or transaction that occurs outside of the blockchain ledger. This can include traditional financial transactions, private contracts, or any other activity that is not recorded on the blockchain. Off-chain transactions can be faster and more scalable because they do not require the consensus of the blockchain network, but they may lack the security, transparency, and immutability of on-chain transactions.