This document provides an overview of encryption, including its history, types, methods, and uses. It discusses how encryption works by converting plain text into ciphertext using algorithms and keys. The main types of encryption covered are manual, transparent, symmetric, and asymmetric encryption. Symmetric encryption uses one key while asymmetric uses public and private keys. Encryption methods fall into two categories: stream encryption which encrypts text character by character, and block cipher encryption which encrypts in blocks. Encryption is used to protect information on computers and in transit, as well as for confidential medical and transaction records, emails, and digital signatures.