Anyone know why it is called rainbow table? Just remembered we have learned there is an attack called "dictionary attack". Why it is not call dictionary?

I was reading a few articles on salts and password hashes and a few people were mentioning rainbow attacks. What exactly is a rainbow attack and what are the best methods to prevent it?

let's just assume a simple non salted hash function, just a plain old $hash = md5($pass). Premises: the password hashing all takes place server side, and the hashes are stored in the database. T...