Summarize what a Blockchain is in a single sentence.
A blockchain is a decentralized and distributed digital ledger used to record transactions across numerous computers, ensuring transparency and security through cryptographic means.
Complete the following task based on the instruction and optional input provided.### Instruction:
Summarize what a Blockchain is in a single sentence.

### Output:
A blockchain is a decentralized and distributed digital ledger used to record transactions across numerous computers, ensuring transparency and security through cryptographic means.