"Shotgun Start": Normally when you start a round of golf you start out on the first tee. What if you have a large group of say 30 golfers or so, and you all want to start play at the same time. You could all spread out on the golf course, and everyone start play at a different hole. In order to all start at the same time you would need some kind of signal to start everyone. Why not use a shot gun, and tell everyone to start at the shound of the gun.
"Scramble": I am not sure but I think a scramble is when you play in groups of 3 or 4 or so. Everyone hits their first ball from the tee. Then you see who had the best shot, and everyone's second shot is taken from the point where the best shot landed. You continue in this manner, playing from the point of the best shot.
I am not a golfer, but my Dad, brother, and uncles all play.