Blockchain is the technology and concept that underpins cryptocurrencies, providing a secure and transparent method for recording transactions.  

At its core, a blockchain is a decentralized digital ledger that records transactions across multiple computers. Unlike traditional databases managed by a central authority, blockchains operate on a peer-to-peer network, enhancing security and making manipulation or fraud difficult. Each transaction is grouped into blocks linked chronologically, forming a chain. 

Key Features of Blockchain 

Decentralization 

Blockchain's decentralized nature means no single entity controls the entire database. This distribution enhances security by eliminating a single point of failure that hackers can exploit. 

Immutability 

Once a transaction is recorded on the blockchain, altering it is nearly impossible. Each block contains a unique cryptographic hash of the previous block, ensuring the integrity of the data. 

Transparency 

Blockchain allows all participants to view the entire transaction history, fostering trust as anyone can verify transactions. While transaction details are public, individual identities are typically anonymized. 

Security 

Blockchain uses advanced cryptographic techniques to secure data. Each transaction is encrypted and linked to the previous one, creating a secure chain that resists hacking attempts. 

How Does Blockchain Work? 

1. Transaction Initiation: A user initiates a transaction, which is broadcast to the network. 

2. Verification: Network participants, known as nodes, verify the transaction's validity. 

3. Block Creation: The verified transaction is bundled with others into a new block. 

4. Consensus: A consensus is reached among nodes to add the new block to the blockchain using mechanisms like Proof of Work (PoW) or Proof of Stake (PoS). 

5. Transaction Completion: The transaction is recorded on the blockchain and is accessible to all participants.