Hash is a small piece of code that takes some input and outputs an encrypted fixed-length line of text. Some very interesting facts about hashes are that they are impossible to decrypt; the only way to do so is to have the original information that produced the hash, which is the whole point of them.

When a block in the blockchain is full, a hash based on all of the information in the block is generated and passed onto the next block as a connector between the two, and attempting to change any single bit of information in a block results in a new hash, breaking the chain and rendering it useless, which is why it's tamper-proof.

A hash in blockchain is a unique fixed-length alphanumeric string generated by a cryptographic algorithm to represent data. It serves as a digital fingerprint, ensuring data integrity and security. Even a minor change in the input data produces an entirely different hash, making it tamper-evident.

Hashes are critical in blockchain operations. They link blocks by including the hash of the previous block, creating an immutable chain of records. This mechanism ensures data consistency across the decentralized network.

Popular hashing algorithms, such as SHA-256 (used in Bitcoin), are designed to be fast, irreversible, and collision-resistant. Hashes are also essential in validating transactions and mining, providing the foundation for trust and transparency in blockchain systems.