Hashing is the transformation of a string of characters into a usually shorter fixed-length value or key that represents the original string.

For example SHA-2 Hash of above statement will be 696421ad8a148a5e4c4064b9c9191831b6bed4aa484b2ccebe3208184bb30b29

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Other hashing are MD5 and SHA-1 (previous version of SHA – 2).

Importance of Hashing Functions can be judged based upon there use cases
1) BlockChain Powered BitCoin (Digital Currency) core is SHA-2 Hash.
2) Digital Signature for Documents.