Transactions between people get written down on a ledger (single page).
These then get collected into a single block.
This block is added to a chain of blocks. Now we have a block-chain!
Blockchain can be defined as a "digital, decentralized and distributed ledger in which transactions are logged and added in chronological order with the goal of creating permanent and tamper-proof records." Put simply, a blockchain is a shared ledger of data — e.g., transactions or code — that are batched into blocks, verified, and subsequently accepted as part of the blockchain by a network of distributed users (nodes) through a consensus mechanism. Because each block of verified data contains a unique signature of data from the previous block, they are inextricably linked together into a “block-chain.” A network-based consensus mechanism is the way a blockchain protocol agrees on how its underlying technical architecture will operate.
In other words, blockchain offers a digital, open-source peer-to-peer transaction system where records are decentralised and spread across a network of users. Essentially, blockchain is a new approach to database architecture; where “[it is] an improvement over the way that, traditionally, databases have been designed and used in the past,” noted Morgan Stanley (2016).
This timeline spans the inception of blockchain protocols to more recent innovations like smart contracts.
Blockchain relies on a decentralized network of users to validate and record transactions instead of a central authority. This characteristic makes blockchain transactions immutable, transparent, constant, fast, secure, inexpensive, and tamper-proof.