Encryption takes data in its original (plaintext.) form and uses a mathematical algorithm (cipher) and an encryption key to transform it into an unreadable form (ciphertext).
Decryption takes ciphertext and transforms it back into plaintext, which once again uses the cipher in conjunction with a key.
What do you think of when you hear the word encryption?
Is it spies sending their superiors information in secret code?
Perhaps you visualize windowless rooms in some secret government facility where pale, bespectacled code-breakers pour over secret messages and try to decipher them?
This might happen in the movies, but the code-breaker today is just as likely to be a 14-year-old script kiddy, and the secret facility his bedroom.
He enjoys a slice of pizza and listens to his pirated music collection while he uses tools written by a real hacker to crack the encryption on your network.
Encryption is an incredibly useful security tool.
It can prevent crackers from sniffing information on your WLAN, it secures authentication of computers and users, and it can protect data on hard drives.
However, not all encryption is created equal.
Some methods are stronger than others, and even strong encryption can be undermined by poor implementation or improper use.