ROT13 (short for "rotate by 13 places") is a simple cipher algorithm that replaces each letter in the alphabet with the letter 13 positions ahead of it. The algorithm is named after the fact that the letters are "rotated" by 13 positions

To understand how ROT13 works, it is helpful to look at an example. Suppose we have the message "HELLO WORLD". To encrypt this message using ROT13, we would replace each letter with a letter that is 13 positions ahead of it in the alphabet. Using this rule, "H" would become "U", "E" would become "R", "L" would become "Y", and so on. After applying this substitution to the entire message, we would end up with "URYYB JBEYQ".