Add dvd to iTunes library???

What sort of DVDs? If you mean commercially released films or TV shows on DVD I'm afraid that can't be discussed as that involves breaking the encryption on them (which is illegal in most countries). Such discussions are against the terms of use. "Do not submit software or descriptions of processes that break or otherwise ‘work around’ digital rights management software or hardware. This includes conversations about ‘ripping’ DVDs or working around FairPlay software used on the iTunes Store.":
Discussions Help & Terms of Use
US Code, Title 17 Sec. 1201. Circumvention of copyright protection system

i mean i own it when i buy it right?

Sort of.
You own the physical DVD but you do not "own" the material on it.
When you purchase a DC/DVD, you are purchasing a license to listen/watch it.
The copyright owner (music label or movie studio) retains the rights to copy it.

In order to copy a commercial DVD, you need to break the encryption used on it.
According the DMCA (Digital Millenium Copyright Act), breaking the encryption is illegal (even if you own the DVD).

You can save the data file where ever you want. You can burn it to a DVD for back up purposes (note: this is not a DVD you can play in a standard DVD player). You can, however, only play the movie on an authorized computer (you can have up to five) an iPod, iPhone or Apple TV.

Best of luck.

do you think a movie bought on itunes then burned to a dvd would be playable on a PS2?