Cryptographic Hash Function
A cryptographic hash function (CHF) is an algorithm that maps data of arbitrary size and type (numbers, alphabets, media files, etc) to an alphanumeric string, or hash.
The CHF is a one-way function, meaning that it is very hard and highly improbable to determine what the original data was if you are given just the string of hashes. The only way to crack a CHF is through various types of brute-force searches.
It cannot be be stressed enough: cracking a CHF is nearly impossible. Consider the following thought experiment. If you had a glass full of sand and then poured it out on a table, it would probably be easier to determine the order of which sand particles came out of the glass than to crack a CHF.
Almost all cryptocurrencies use a CHF to encrypt transaction data and keep that information private and secure. Bitcoin uses a CHF called SHA-256.