Eli5: how does encoding/decoding with a keyword work?

Question

I have watched so many documentaries about decoding but I didn’t understand very well. What I know is move the letters of the word to the front of the alphabet and then move by 1 each time. Example with the word ‘coin’

C O I N A B D E F G H J K L M P Q R S T U V W X Y Z
O I N A B D E F G H J K L M P Q R S T U V W X Y Z C
I N A B D E F G H J K L M P Q R S T U V W X Y Z C O
… and so on so forth but how do they know which letter is which.

In: Other

Answer 1

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