Hash is a function created using an algorithm that converts data of arbitrary length to a fixed-length.
It is a fixed-length alphanumeric code used to represent a word, message, or data that serves as a fingerprint or summary of digital data. Hashes have basically two characteristics: a) the same input will always produce the same output, and b) there is no function or way to reverse the output back into input.
In cryptography, hashing means the process of creating a fixed-size output from a variable-size input. This is accomplished through the use of hash functions, which are mathematical formulas (implemented as hashing algorithms).
Hashes are useful for confirming the correctness of information without revealing the information’s content. The Bitcoin blockchain, for example, comprises several processes that involve hashing, which are critical in the mining process.