If you write something down that is important, private, or sensitive you might worry that someone else is going to read it. If you need to give it to a messenger to take to another person, the risk of the wrong people reading that message increases. Encryption changes the composition of a message or data so that only people who know how to return it to its original form can read it. To anyone else, it’ll appear as gibberish or a meaningless collection of characters and symbols.