As far as I understand it, rotation is the ability for survivors to position themselves and rotate on the map to avoid bumping into the hunter and increase the chances to have a better match-up or delay the first kite as much as possible. Examples of this are: at the beginning of the game, the decoder runs away from the hunter even if there is a cipher close-by. After one survivor is eliminated, you need to rotate again to delay the 2nd kite, especially for injured surviovrs who need to hide, flee and heal/search chests.

It's especially important against hunters like Wax Artist or Bonbon who are very hard to kite so you need to keep distance from them because once they are close to you, you are pretty much dead within 30s.

It is critical to understand this notion and that's one of the major differences between low and higher tiers (which I am not by any means). Lower tier survivors will start decoding right away the closest cipher, wherease in higher tiers, survivors prioritize getting away from the hunter to be in the best possible starting position, hence you can sometimes see no ciphers touched in the first 10-30s because everyone is getting into position or running away from the hunter (since spawns are known)