A cipher is a series of operations which transforms something which can be easily understood into something which is very hard to understand. A cipher is used to "encrypt" a message so that it won't be able to be understood if it gets into the wrong hands. The cipher is also used to "decrypt" the message so that it becomes readable again. There are many famous ciphers such as the rail fence cipher, 11B-X-1371 and the Beale ciphers. Below is part of a famous runic cipher found on the Kensington runestone.
What does this cipher do?
This cipher runs a very simple set of operations which turn a set of alphabetical characters into a series of numbers: for each letter of the alphabet, replace it with the numerical position of that letter. So, for example, the letter A gets turned into 01, the letter B gets turned into 02, the letter C gets turned into 03, and so on up to Z which is turned into 26.