What is a hybrid SACD?


Hi guys, just purchased a Bob Rodriquez Jazz 'Corridor' cd from the local thrift store, and on the back it says 'this hybrid SACD'......., as I have never bought a cd like this before can someone please clarify for me what a hybrid cd is? The sound quality is excellent. Does that also mean a full SACD will sound even better?
Thanking you in advance.
128x128gawdbless
2 layers are on the CD... an SACD layer for sacd players as well as the commmon red book CD layer that is playable for non-sacd players. Easy enough.
I think we need to say how the lower layer can be "seen" if there is another layer on top of it.

The CD and the SACD playback lasers are different wavelengths (colors). The top layer is transparent at the wavelength used for reading the lower layer.