Rotate 13 is a simple Caeser cipher: https://en.wikipedia.org/wiki/Rot13 A half-alphabet rotation of 13 is chosen for simplicity, because then the encryption function is the same as the decryption function. This is easy enough to do by hand, but there are numerous utilities and even JavaScript applications (like https://rot13.com/ ) that can do it quickly. The point is to prevent someone from reading something accidentally, like spoilers to movies or punchlines to jokes. Sometimes asking Google is faster than asking me.
Rotate 13 is a simple Caeser cipher: https://en.wikipedia.org/wiki/Rot13 A half-alphabet rotation of 13 is chosen for simplicity, because then the encryption function is the same as the decryption function. This is easy enough to do by hand, but there are numerous utilities and even JavaScript applications (like https://rot13.com/ ) that can do it quickly. The point is to prevent someone from reading something accidentally, like spoilers to movies or punchlines to jokes. Sometimes asking Google is faster than asking me.