I have already answered this but I don't know where it went so I will answer again.
They are all cams and they all possess varying degrees of cam properties which are:-
Lift
Duration
Rise/Fall Rate
Overlap (when using more than 1 cam)
Cams convert rotary motion into reciprocating or sliding motion
1 is a very light weight cam that will not tolerate load and would only be used in very light linkage applications like system switches. Where movement is slow and limited
2 Is the automotive design and is used in petrol and Diesel engines. It is capable of very high loads and speeds. These cams can be designed for varying amounts of lift and duration so are suitable for racing engines too. They are used to operate multiple valve designs and the in the case of diesels they lift the high pressure pumping elements in inline injection pumps.
3 These are used where a relatively small rotation is translated into a much larger sliding, reciprocating motion, such as the piston linkage on a steam train.
4 These cams are shaped like a comma and have a steady rise rate and a very rapid fall with virtually no duration. They were used in the old fair ground steam organ in controlling steam to the organ pipes. The note would have a steady rise and attack and very limited sustain and reverberate causing the distinct sound
