A blockchain is a distributed ledger technology that stores and records data in a secure, distributed, and immutable way. It is a public ledger of all transactions that have ever taken place in a particular cryptocurrency. A cryptocurrency is a digital asset designed to work as a medium of exchange using cryptography to secure the transactions and to control the creation of additional units of the currency.
For example, Bitcoin is a cryptocurrency that runs on a blockchain. The Bitcoin blockchain is a public ledger of all Bitcoin transactions that have ever taken place. It is secure, distributed, and immutable, meaning that the data stored on it cannot be altered or deleted.