Blockchain is a decentralized digital ledger technology that securely records transactions across multiple computers. This ensures that the data is transparent and tamper-proof, as each block contains a cryptographic hash of the previous block, linking them together in a chain. 

Key features include:

1. **Decentralization**: Unlike traditional databases, blockchain operates on a peer-to-peer network, reducing reliance on a central authority.

2. **Transparency**: All transactions are visible to participants in the network, promoting trust.

3. **Security**: Cryptographic techniques safeguard data integrity, making it difficult to alter past records.

4. **Immutability**: Once a block is added to the chain, it cannot be changed without altering all subsequent blocks, ensuring the permanence of records.

Applications range from cryptocurrencies like Bitcoin to supply chain management, voting systems, and smart contracts. Its potential continues to grow across various industries, driven by the demand for secure and transparent systems.