Look up at the top of the page where your screen has a link to "FAQ/How to's" and go there. You'll find it listed in two parts because it's the only mod so popular as to need two parts to hold all of the comments.
Yes, it's '09 compatible. In fact, the '09 needs it just as badly as all the previous years. The basic concept is that you put some sort of hard to penetrate screen inside (usually) the front grill to protect the soft aluminum AC radiator from flying stones and road debris. Some use a flexible plastic screen used to keep leaves out of your home's gutters, others use metal screen. I'd call it a "must have" accessory and give Honda one of their very few black marks for not taking care of the problem at the factory.