If you’re even somewhat-knowledgeable about digital photography, then you know what RAW is.  And, if not, you can find out more in this article on Wikipedia.  Basically, it’s the raw, pure data from the camera’s sensor rather than the processed, cleaned-up and compressed data that you get from a JPEG.  All dSLRs and high-end point-and-shoots and bridge cameras give you the option of shooting in RAW and you should, in my opinion, always take said option–it gives you so much more latitude in post-processing than a JPEG.  Want to bring out those shadows or punch up those colors?  You’ll get better results from a RAW image.  Here’s a flowchart I recently spotted on pixiq.com that best summarizes the “why?”: