To expand on you last question ...

The RAW files themselves hold all the information that the camera has captured without any editing. These files are a lot larger as they contain data only. This is like having a canvas, paints and brushes; from here you have a lot of flexibility to create any image.

A JPEG file has been processed and compressed and contains a lot less detailed, most importantly it had been created as an image. This is like having a finished image created and given to you in a frame.

If you have the RAW files, you can do a lot more changes and corrections. If you have the JPEG you are very limited by the amount of editing you can do. Like in the picture analogy, you can amend it only so much.

There are a number of reasons why photographers do not give out RAW files (off the top of my head): * They are data only and not really viewable as an image * You pay the photographer to create pictures from the RAW "materials" (file), the end result you want are the pictures * If it went to copyright claims, the person with the RAW files can slow ownership etc.