In simplest terms - perhaps oversimple - the RAW format amounts to storing the entire image information file
UNPROCESSED - precisely the data recorded by the camera. Technically, a RAW file is not an image file, it is information from which an image file may be rendered. That is why special software is necessary to work with RAW files; first you have to turn the data into an image file of some sort. You could think of a RAW file as being, analogous to film terms, equivalent to an undeveloped negative. Only with some processing of the undeveloped negative may you obtain a template from which an image may be made. Camera manufacturors generally provide proprietary software for this purpose, "developing the negative", and some 3rd-party software vendors offer RAW-capable product, including but not limited to Adobe's PhotoShop.
I would say that for all but the most critical, commercial production or extremely serious amature competition purposes, the RAW format offers little if any practical benefit, while imposing the costs of vastly increased storage capacity and additional processing software.
Sorta kinda like having a 900HP car capable of sustained speeds in excess of 225MPH, or an over-the-road tractor capable of pulling 40-ton loads at highway speeds - neat, fun to have, mebbe, but not particularly practical to the average individual, and most unlikely ever to used by other than professionals to capacity and purpose in day-to-day application.
Noted digital photographer Keith Cooper offers a good discussion of the pros and cons, why's and how's, where's and when's of RAW format
HERE
Google's free
Picassa supports some RAW processing, though it is not compatible with all camera manufacturor's implementation of the RAW format. I've found it does work with both Nikon and Canon RAW files - at least to some extent.
IrfanView also has limited RAW functionality.
Anyhow, I wouldn't wory about RAW much in your situation, and I certainly wouldn't recommend you buy any software specifically on the basis of RAW support. The Nikon software that came with the camera likely will give you all the RAW capability you'll need - or even want - for a good long while to come.