What.
The word "passphrase" is used to convey the idea that a password, which is a single word, is far too short to protect you and that using a longer phrase is much better.
Why.
Using passphrases made of randomly-chosen words can be both easy to remember and hard for someone else to guess, which is what we want out of a passphrase.
How.
Using the EFF long wordlist, we simply use PHPs array_rand() function to select 5 random words from the wordlist to generate a secure, random passphrase.