What Is a Blockchain?

 A blockchain is an open, distributed ledger that records transactions in code. In practice, it’s a little like a checkbook that’s distributed across countless computers around the world. Transactions are recorded in “blocks” that are then linked together on a “chain” of previous cryptocurrency transactions.

“Imagine a book where you write down everything you spend money on each day,” says Buchi Okoro, CEO and co-founder of African cryptocurrency exchange Quidax. “Each page is similar to a block, and the entire book, a group of pages, is a blockchain.”

With a blockchain, everyone who uses a cryptocurrency has their own copy of this book to create a unified transaction record. Each new transaction as it happens is logged, and every copy of the blockchain is updated simultaneously with the new information, keeping all records identical and accurate.

To prevent fraud, each transaction is checked using a validation technique, such as proof of work or proof of stake.