Can someone explain to me what a clavinova is and why it is different from a regular digital piano?Do they devaluate as fast as a regular dp?

clavinovas are just a brand of DPs from Yamaha, i.e. CLPs or CVPs, and they are digital pianos. what do you mean by 'regular DP' or if you mean the additional synth functions and voices as on CVPs?

Yep, Clavinova is just Yamaha's high-end line of digital console pianos, much like the HP series is to Roland. They generally have a better action, sound, user interface, cabinet design, etc. Otherwise, they are "normal" digital pianos.

Clavinovas do seem to hold their value well [for a digital piano] but that is probably just because they are so expensive to start with. In my opinion, they depreciate just as fast as any digital piano, but the used prices are higher because of the higher initial value. I still wouldn't waste my time on a 10-year-old Clavinova though, regardless of the original price. Technology is as such that a current entry-level YDP series (Clavinova's little brother line) will sound and feel better than an old Clavinova.

No I can't explain it because it is just a "regular digial piano". It is Yamaha's high end line of home pianos. They also have a line of lower priced home type pianos (called Aris, or YDP) the two lines overlap in features. The clavinova line does tend to use a bit more wood and less plastic in the cases but still it is mostly particle board with plastic laminate finish but better quality on the more expensive models.

Yamaha also makes a line of stage pianos that currently have some features not present in the Calvinova. Yamaha also makes a portable version of the Clavinova intended for home, not stage use, The P155.

Roland and Kawai make models that are very comparable to the Clavinova line

One thing that is different about the Clavinova, at least in the US is that Yamaha keeps them out of the big discount chain stores so there is not so much competition and they can be sold at higher price. This is Yamaha's way of supporting their dealers. But inside the sound and key action is mostly the same as found in other Yamaha digital pianos.