How to Explain Blockchain, Cryptocurrency, and ICOs in one short paragraph Elevator Pitch:
A blockchain is a secure distributed ledger or database where past “blocks” of entries are “locked in” so securely that you cannot alter them. It is not run by a company or any trusted party—but a computer network. A network of computers reach a consensus on the current block of transactions and once a majority agree, the new block of transactions is locked onto the blockchain database. It’s a virtually unhackable, highly secure distributed ledger that can replace intermediaries like banks, or any company and authority now relied on as “trusted party” or controller of an information system. With “Smart contracts” in the blockchain system, executed by the computer network when agreed upon conditions are met, you can conduct transactions without lawyers and middlemen. Blockchain is used for virtually unhackable digital currency to pay for online transactions (cryptocurrency—like Bitcoin, Ether, others) and for a new means of raising funds: an “Initial Coin Offering” where you produce a “token” you can trade on a blockchain that, combined with Smart Contracts, provides rights to buyers to use services or buy products.
However, this is useful if you are presenting something in connection with this subject, and someone asks you what is blockchain, in this case this can be your quick answer to that question.