Blockchain
In short: A blockchain is a type of distributed ledger technology: a shared record of transactions that many computers, called nodes, keep in sync.
A blockchain is a type of distributed ledger technology: a shared record of transactions that many computers, called nodes, keep in sync. Transactions are grouped into blocks, and each block includes the cryptographic hash of the previous one, linking them into a chain.
Why it matters
Because every node holds a copy and the blocks are linked, changing an old record would mean rewriting every later block and convincing the rest of the network, which is extremely difficult on a large network. This lets people who do not know each other agree on who owns what without a central bookkeeper. Blockchains power cryptocurrencies, smart contracts and tokenized assets, but they involve trade-offs in speed, cost and privacy, since most public chains are transparent and every node processes the same data.
Example
When you deposit coins to an exchange, your wallet broadcasts a signed transaction to the network. Nodes check the signature and the balance, and a miner or validator includes the transaction in a new block. Each block added afterward counts as another confirmation, and the exchange credits the deposit once the required number of confirmations is reached. Anyone can follow the whole process on a block explorer by searching for the transaction ID.