To complete the great description of what is a RAW file, I will explain how I use it.
It is very rare to me to to give or sell the RAW file. It happeneds only ones in my carrier because my client was managing a team of 20 photographers for only one client, so she had to create a common style to everyone. The style of each photographer was not requiered that time.
Usually, Raw files stay under my only management. They are my images ! I’m an author ! So, I decide my development, exposition, contrast, colors, balance, or everything I judge necessary to complete my image to be displayed when it’s for my own project, or delivered to and used by my clients.
I usually do not allow reframing, color or any other adjustment from my images. If my client have a special request he has to pass true me.
SO, because they do not have the right to make a post processing, they do not need RAW files.
Also, as Fabien said that RAW allows for non-destructive post-processing. To explain it in a simple way (I hope), it means that when you take a photo, your RAW file create a large quantity of layers. And each of them contain a wide range of possible adjustment. For exemple, if you take only the layer of exposition, your Raw write your adjustment like +/_ 0 as you set on your camera, but also write a larger one +1, +2 and -1, -2 (not really, but just to make understand). Then when you are on lightroom or any other soft to develop your image, you can access to all the information from -2 to +2… And this for each layer.
In final, Raw file are much heavier and are great consummer of hard drive capacity, because the content more informations.
If you compare a developpement from a JPEG file, you can not get the same quality because all the layers wrote in the RAW are compressed in only few or sometime only one layer (depending on the type of jpeg compression). Because the informations are flat, when you tried to adjust, it destroy the image itself by recreating new information and you get JPEG atefact visible on your image (square colored or other types). In raw, we use what exist already in the file so it do not alterate image.
As Fabien said (again), Raw file also content all the information of the image, my copyright and my metadata, (ITPC and EXIF). These data are under my sole property and I do not allow anyone to access to it.
Clients can read it because they are integrate to my TIFF or JPEG files, but they can not transform.
It’s a bit like the nega for the film.
When I shoot, I use only RAW, I never double it with JPEG.
I hope my Fr-english is readable.