The document provides an overview of encryption, including what it is, why it is used, and how it works. Encryption is the process of encoding information to protect it, while decryption is decoding the information. There are two main types of encryption: asymmetric encryption which uses public and private keys, and symmetric encryption which uses a shared key. Encryption is used to secure important data like health records, credit cards, and student information from being stolen or read without permission. It allows senders to encode plain text into ciphertext using a key.