Blockchain is a distributed ledger that records transactions in a way that makes it difficult or impossible to change, hack, or cheat the system. It allows digital information to be recorded and distributed, but not copied. This makes blockchain secure and transparent. Blockchain uses cryptography to let users make transactions securely without needing central oversight. It has the potential to disrupt many industries by replacing intermediaries and cutting costs of transactions. Examples include financial services, digital asset transfers, and smart contracts that self-execute based on predefined rules and conditions.