A one-way hash function is a mathematical function that generates a fingerprint of the input, but there is no way to get back to the original input. If the input is the same then the hash is always the same, if it changes at all, even by one character the output hash is completely different. A hash can be used to verify that input A is identical to input B but cannot be used to get the input back from the output like with another mathematical function, encryption.
One-Way Hash Function
