Blockchain is a decentralized, digital ledger technology that records transactions and data across a network of computers in a secure and transparent manner. It's the underlying technology behind cryptocurrencies like Bitcoin and Ethereum, but its applications extend far beyond digital currency.

Here's how it works:

1. A network of computers is established, each with a copy of the blockchain.

2. When a new transaction is made, it's broadcast to the network.

3. The transaction is verified by special nodes on the network called miners.

4. Once verified, the transaction is combined with other transactions in a batch called a block.

5. The block is added to the blockchain, which is updated on each node.

6. The blockchain is secured through cryptography and consensus mechanisms.

Key features of blockchain include:

1. Decentralization: No single entity controls the blockchain.

2. Immutable: Transactions can't be altered or deleted.

3. Transparent: All transactions are publicly visible.

4. Consensus: Nodes agree on the state of the blockchain.

5. Security: Cryptography protects transactions and the blockchain.

Blockchain applications include:

1. Cryptocurrencies (Bitcoin, Ethereum, etc.)

2. Supply chain management

3. Smart contracts

4. Identity verification

5. Healthcare record management

6. Voting systems

7. Cybersecurity

In summary, blockchain is a powerful technology that enables secure, transparent, and decentralized data management, with far-reaching potential across various industries.