A Bitcoin hash is a fixed-length string of characters that represents data from a block in the Bitcoin network. Using the SHA-256 (Secure Hash Algorithm 256-bit) cryptographic function, the hashing process converts input data into a unique alphanumeric code. Each block in the Bitcoin blockchain has its own hash, which is created from the block’s header information, including the previous block’s hash, timestamp, and transaction data.

This ensures that any alteration in the block’s data will result in a completely different hash, providing a level of security and integrity. Hashes serve two main purposes. First, they link blocks together in a secure manner, forming a chain that prevents tampering.

If someone tries to change a block, all subsequent blocks would need to be rehashed, disrupting the entire chain. Second, hashes play a role in the mining process. Miners compete to find a hash that meets specific difficulty criteria, which involves repeatedly hashing the block data with different nonce values until a valid hash is found. This process confirms transactions and adds new blocks to the blockchain.