hybrid and redbook

could you please explain what hybrid and redbook cd`s are?
could you play them on a regular cd player,do they sound better than a regular cd?
Redbook is a normal CD. It will play on any standard CD player, DVD player, or SACD player.

Hybrid's are the new SACD (Super Audio CD) titles which have two "layers". The outermost layer, which is the only one that a conventional CD player can read, is a Redbook layer which plays on any ol' CD player. Then underneath that layer is data that can only be read by a DVD transport which has the proper lens and laser wavelength. That data is encoded in DSD and playable only on a SACD player. Hybrid's are designed to enable you to enjoy these titles on any CD player, but if you upgrade or take them to a friend's house and play them on a SACD player, you will enjoy superior sound.

There is some debate about whether the Redbook layer on hybrid discs sound better or worse than standalone Redbook titles. The few I've heard sound fine, although in some cases there are other Redbook versions I prefer (XRCD for example)