In terms of what each shot does....
A "punch" shot is a shot with only a little swing through the ball, so that the ball is effectively punched out of its lie. The result of this is that the ball flies at a much lower trajectory than a Full shot (therefore, less affected by wind) and will tend to roll more on landing (although this can be largely negated with a lot of backspin).
A "chip" shot is similiar to a punch shot in that it is a shot with a low trajectory and a lot of roll. The difference being that the punch shot can be used anywhere from 200yds in, depending on your clubs, whereas the chip shot will be used close to the green. The chip will travel in the air approx. a 1/4 of its distance, with the other 3/4 being the bounce and roll on the green. Great care should therefore be taken that you don't chip when you have an obstruction in the way that will stop the ball from rolling i.e too much rough to get over before you reach the green.
The pitch has more loft than the chip, and will usually carry about half of its total distance in the air, with the rest of the distance being made up of bounce and roll. Again, it is a shot that should be played close to the green.
Lastly, the flop. This shot is played mostly through the air, with about 3/4 of it total distance being spent airborne. It can be played with full backspin which, depending on the circumstances of the green, can result in stopping almost dead where it lands on the green. This is a good shot to use if you are in green-side rough, but have a significant amount of rough to get over before you reach the green.
Hope that helps :-)