With the exception of new characters in Kum Haehyun and Raven, the Revelator demo lets you try out “Episode,” “Versus,” and “Training” modes with 20 of the game’s characters.
For more info, Episode mode lets you pick a character and fight against CPUs while enjoying the prequel story of the console version of Guilty Gear Xrd: Revelator. Versus mode lets you play offline with one or two players. This can be done with another player or CPU opponent.
And finally, Training mode is the usual Training mode, except with some new additions that are being added to the game that lets you freely practice your combos. This mode also supports two players so you can have some sparring sessions while practicing.
Guilty Gear Xrd: Revelator will release in Japan on May 26 for PlayStation 4 and PlayStation 3. North America will get the game on June 7, and Europe on June 10, 2016. The North American demo from pre-orders will go live on April 5. As mentioned by Code in the comments, you’ll need to pre-order the Japanese copy of the game to try out the demo, so you might want to wait a few more days for the North American one unless you were already planning on getting the Japanese version.