From Jonathan Gardner's Tech Wiki
Cryptography is the art of hiding data.
Today, it focuses on two important features:
- Encryption: The art of hiding data that can be later recovered if you only know how to do it. Usually, this is a method that involves an encryption algorithm and a secret key.
- Digital Signing: The art of providing a checksum that can uniquely identify data.
Cryptography for Dummies
Here's a short article that describes how encryption works: Encryption for Dummies