In computer science, a hash is a function that takes arbitrary binary data and converts it into a fixed-length digital fingerprint. The size of the hash (usually measured in bits) needs to be large enough that its vanishingly unlikely for you to get a match by chance. In recent years, some clouds have begun to cast a shadow over the Merkle-Damgrd system. NIST announced a public competition to deliver Secure Hash Algorithm 3 (SHA-3)”]
Source: https://nakedsecurity.sophos.com/2012/10/04/sha-3-hash-competition-concludes-keccak/