Encoding, Encryption, Hash

Encoding
Use to change the format of the code to different format for usability. The encoding technique is public, so any one who know how to read can get the information.

Encryption
Use for security purpose. We can encrypt the data using key to make it unreadable by people who don't have the key. If we want to read the data, we need to decrypt it using the key.

Hash
Use to check the integrity of the data. By hashing the same data, it will always yield the same result. However, we cannot transform the hash data back to the original one.