Many people tend to think of Encryption & Hashing being one and the same :(
Encryption and hashing are completely different. With encryption, you have the ability to decrypt. Its usage is like a you encrypt the text, you will be able to decrypt, whether it is with one symmetrical key or with a pair of keys.
Hashing is a one-way function. When you hash a value, you are always guaranteed to get a certain result. But with that result, you will not be able to reverse it and retrieve the clear-text. Also with hashing, the size of the hashed data will always be a certain sized specified by the hashing algorithm.
When to use encryption versus hashing depends on the application. Hashing is fast and only one-way. That's the key difference. One-way versus Two-way.