Cryptography is the study of communication that must be kept secret from bad actors. Hashing is a mathematical operation whereby an input is changed to an output, known as a hash. This is done in such a way that the process to undo it is significantly more difficult than the process to create the hash, thus the only efficient way to determine what the input was is to test inputs until the the correct one is guessed, this is known as a one way function. This process is very useful for anything that needs its authenticity verified, such as password or files. Currently there are several cryptographic hashing algorithms that aren't considered secure anymore, but are still commonly used including MD5, RC4, and SHA-1. Encryption uses similar concepts, but a special value like a password, or key can be fed into the function along with the encrypted data to get the original data back.