Unfamiliar with your camera, however generally (and you should check the manual)
"A" would be aperture priority mode, in this mode you tell the camera what aperture you wish to shoot at and it determines the shutter speed.
"S" would be shutter speed priority mode, in this mode you tell the camera what shutter speed you wish to shoot and it determines the aperture.
If your now asking "Whats an aperture" I would suggest picking up a book on general photography such as "Understanding Exposure"
Taking images in RAW instead of JPEG is not for everyone, unless you own photo editing software and enjoy spending time editing images after taking them stick with JPEG.