It mostly tells the story and the game mechanics of the game. The Gokaiger go to a planet that supposedly has great treasure on it, but then their Ranger Keys get scattered all over the planet. So now they have to find the keys while fighting the Zangyack that are there...for some reason.
It looks like you'll be playing Gokai Red most of the time, but there are mini-games where you play as the other Gokaiger. The basic goal is to find all the Ranger Keys, either by completing mini-games or completing maps, which lead to new areas. You can also Gokai Change into the past Sentai members (I don't know if this can apply to the other Gokaiger and not just Red).
And the article hints that you may get to play as Gokai Silver, too.
Oh, and a Ranger Key will be included in the game for those who get the game first, as usual.