Blockchain is a distributed ledger technology that underlies many cryptocurrencies, including Bitcoin. It is essentially a chain of blocks, where each block contains a list of transactions. Here are some key features of blockchain:

1. Decentralization: Blockchain is typically maintained by a decentralized network of nodes (computers) rather than a central authority. This makes it resistant to censorship and tampering.

2. Transparency: Transactions recorded on the blockchain are visible to all participants, ensuring transparency and trust in the system.

3. Security: Once a block is added to the blockchain, it is extremely difficult to alter the information within it, making it highly secure.

4. Consensus Mechanisms: Blockchains use consensus mechanisms, such as Proof of Work (PoW) or Proof of Stake (PoS), to validate and confirm transactions.

5. Smart Contracts: Some blockchains, like Ethereum, support smart contracts, which are self-executing contracts with the terms of the agreement between buyer and seller directly written into code.

6. Use Cases: Besides cryptocurrencies, blockchain technology has applications in various industries, including supply chain management, healthcare, finance, and more.

Blockchain has the potential to revolutionize many aspects of how we transact and share data, but it also faces challenges, such as scalability and regulatory concerns.