What’s the difference between encryption and hashing?

Encryption is a scheme where an intelligible text (plain text in crypto terms) is made unintelligible (cipher text in crypto terms) using a secure key. Block and stream ciphers and public key systems do this work. The security of the ciphers reside in the key length and decryption process is a difficult without proper knowledge of the key. 

Coming to hashing, they are one-way functions that compress arbitrary length strings into fixed short strings (message digests). Hash Functions can be designed using block ciphers using a secret key as a parameter along with the message that has to be hashed or with out them (dedicated hash functions MD4,MD5, SHA-1 etc..).