A blockchain is a digital distributed ledger. Instead of existing in one place, it is completely managed by computer networks. It uses cryptographic principles to securely carry out and confirm transactions.
By their nature, blockchain records cannot be altered because they are not kept in one single place. This makes them incredibly trustworthy. They also leverage P2P to share records and keep them up-to-date which makes processing much quicker. All cryptos like Bitcoin and Ethereum wouldn’t be able to exist without blockchain technology.