What do you get when you use ProRaw on the new iPhone 13 Pro Max?

I am fairly knowledgeable concerning the use of RAW images on cameras, but I would like to know a little bit more how RAW works on the iPhone. The raw images are much larger then the simple JPGs that we are used to in the iPhone world. In Cameras when I elect to take raw pictures, I also will get a smaller JPG image. In Nikon these raw images have an extension of .NEF and I then get the same image in a JPG format. I other cameras, I get a .DNG raw image.

So, here is what I want to know.... a) what is the extension of the RAW image? b) Can you also get a matching JPG image? c) understanding the sizes of the raw images, how many can you guess you can store on a 126GB iPhone storage and/or 256GB storage?