To encrypt means to convert information into a secret code so that only authorized people can read it. When you encrypt a message, you scramble it using mathematical rules called an algorithm, turning “Meet me at the park” into something like “Xnnk xn rk kyn gryb.” Without the key to unlock it, the message looks like nonsense.

Encryption protects sensitive information like passwords, credit card numbers, and private messages. When you see a little padlock icon in your web browser, it means the website is using encryption to protect your data as it travels across the internet. Banks encrypt financial records, doctors encrypt medical files, and messaging apps encrypt conversations.

The opposite of encrypt is decrypt, which means to convert the coded message back into readable form.

People have encrypted messages for thousands of years. Ancient Roman general Julius Caesar used a simple encryption method where each letter shifted three places in the alphabet (A became D, B became E, and so on). Modern encryption is vastly more sophisticated, using complex mathematics that even powerful computers struggle to crack without the proper key. This protects everything from your text messages to national security secrets.