In a nutshell, Ps CS6 (not "PS 6") is Photoshop 13.x, Photoshop CC is Photoshop 14.x. Photoshop 6 is well over a decade old.
In other words, Ps CC is an upgrade that would have been called Ps CS7, if Adobe hadn't decided to drop the "CS" denomination.
Needless to say, Ps CS6 has been superseded by Photoshop 14.x.
Make no mistake about it, Photoshop 14.x is a MAJOR upgrade, just as CS6 was a major upgrade to CS5.
If Adobe were still selling perpetual licenses (boxed sets or downloads), they would have charged you over $200 to upgrade to Photoshop 14.x.