Encryption is converting data to a format that cannot be read without knowing the key/password used to convert the data. The key used for converting data will need to be supplied to decrypt the data to make it readable. This is a two-way process, encrypting the data and decrypting the data.
Hashing also converts the data to an unreadable format, the difference with hashing is that it is one way and cannot be reversed. This is useful for storing passwords securely in a database, when a user wants to connect to the database they will enter their password which will be converted using the original algorithm that converted the data in the first place to see if the two strings match, if they do match the user is granted access. The benefit of using a hash is that if the converted data was compromised it would not be readable without first knowing the original plain text password.