The purpose of encryption in computer security is to protect sensitive data by converting it into a format that is unreadable to unauthorized users. This is achieved through algorithms that transform the original data (plaintext) into an encoded version (ciphertext). Only those who have the appropriate decryption key can reverse the process and access the original information. Encryption helps ensure confidentiality, integrity, and authentication of data, making it crucial for safeguarding information during storage, transmission, and processing.