https://medium.com/@ahjuice/cryptography-what-is-it-and-how-does-it-work-2a21a730d694

As defined by Bruce Schneier in his book Applied Cryptography, “The art and science of keeping messages secure is cryptography […].” Cryptography, while now considered fundamental in our digital lives, is not specifically related to computing. It has existed in various forms for millennia. From Wikipedia’s article on the history of cryptography:

You have probably seen simple examples of cryptography before. A Caesar cipher, or shift cipher, is commonly used in children’s games which involve decoding a secret message. ROT13 is an extremely common type of shift cipher in which the alphabet is rotated by 13 steps, as illustrated below: