Blockchain is a decentralized and distributed digital ledger technology that securely records transactions across multiple computers. The main innovation of blockchain is its ability to allow digital information to be recorded and shared without the need for a central authority, ensuring transparency and security.

Each transaction on a blockchain is grouped into a "block." These blocks are linked or "chained" together in chronological order through cryptographic hashes, which are unique identifiers generated by a hash function. Once a block is added to the chain, it is extremely difficult to alter the information within it, providing a high level of data integrity and security.

Blockchain operates on a peer-to-peer network where each participant (or "node") maintains a copy of the entire blockchain. Transactions are validated by these nodes through a consensus mechanism, such as Proof of Work (PoW) or Proof of Stake (PoS). In PoW, miners compete to solve complex mathematical puzzles to validate transactions and add new blocks, earning cryptocurrency rewards for their efforts. PoS, on the other hand, allows validators to create new blocks based on the number of tokens they hold and are willing to "stake" as collateral.

The most well-known application of blockchain technology is cryptocurrencies, such as Bitcoin and Ethereum. However, blockchain's potential extends beyond digital currencies. It can be used for a variety of applications including supply chain management, voting systems, healthcare records, and smart contracts. Smart contracts are self-executing contracts with the terms directly written into code, which automatically enforce and execute agreements when certain conditions are met.

Blockchain's decentralized nature, coupled with its transparency and security features, makes it a transformative technology with the potential to revolutionize various industries by reducing fraud, improving transparency, and enabling secure, efficient transactions.