What is Blockchain?

A blockchain functions as a shared database maintained simultaneously across many computers, called nodes. Rather than storing data in a single location controlled by one party, every participating node holds a copy of the entire ledger. This makes the system highly resistant to data manipulation, because altering a record on one node would conflict with the copies held by all others.

Data is grouped into blocks, each of which contains:

• A set of validated transactions or records
• A timestamp indicating when the block was created
• A cryptographic hash of the previous block, forming the chain

Because each block references the one before it, changing any historical record would require recalculating every subsequent block — a task that is computationally prohibitive on large, well-distributed networks.

Blockchains use consensus mechanisms — rules that determine how participants agree on which transactions are valid — before adding new blocks. Common mechanisms include Proof of Work and Proof of Stake.

Blockchains can be public (open to anyone, like Bitcoin or Ethereum) or private/permissioned (restricted to approved participants, as used by some enterprises). Public blockchains prioritize transparency and censorship resistance; private blockchains prioritize speed and access control.

Beyond cryptocurrency, blockchain technology is explored for supply-chain tracking, digital identity verification, voting systems, and contract execution, though large-scale adoption in these areas is still evolving.