Encryption has existed since the dawn of warfare and power. The Egyptians used it as early as $1900$ BCE. The idea is simple. You have information that you only want certain specific people to be able to see. Modern encryption is extremely powerful. Our phones come with encryption built in so that others can$$t take our information. However, some simple information is open for the world to see. An email is like a postcard as it passes through the Internet. Anyone monitoring the traffic can read your message. We would like to be able to keep things private at times.