A transposition cipher is a method of encryption that rearranges the letters of a message to create a coded version. Instead of changing the letters themselves, it alters their positions based on a specific system or key. This means that the original message can be reconstructed if the correct method is known. For example, in a simple transposition cipher, the letters of a message might be written out in rows and then read in columns. This technique can be used to enhance the security of information, making it harder for unauthorized individuals to decipher the original message without the key.