4 were helpful and 1 was rude. Not a bad average, really. Learn to use the ignore button and put that stuff behind you.
As for the RAW question, what the others have said already. Try an experiment though. Shoot the same scene in JPG and in RAW, then open them up in a RAW editor and see how much more you can do with the RAW version. To a significant degree, you can change your exposure settings after the fact, like to bring an over-bright sky back down to more acceptable levels, or to bring something too dark back up, getting detail in either.
I think of RAW as a negative that can be used extensively in a darkroom, while JPG is more like a Polaroid that is whatever it was when it popped out - you're mostly stuck with it. JPG is also compressed, which means that information has been discarded; thrown away just to get a smaller file size. That information is the details you'll never be able to get back.