1. What is the Cam?
A Cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion.
A cam may be defined as a rotating machine part designed to impart reciprocating and oscillating motion to another machine part, called a follower. 

2. How do cams make life easier?
Cams turn rotary motion into up-and-down motions.
Cams allow machines to apply pressure at particular moments in the cam’s cycle. They are used in sewing machines to push the needle and thread through material in regular patterns.

3. Examples For Cams: Camshaft of an Engine
The use of cam and follower systems are vital in engines, where they are used to open and close the inlet valve and the exhaust valve to the cylinder head.
 The cam and follower system is a plate cam and flat follower system, and of course the function of the system is to open and close the valves at the correct time during the four stroke cycle of the engine.
Camshaft of an Engine

4. This system incorporates a rocker arm
This system incorporates a rocker arm. In this case the motion the cam imparts on the follower is translated to the valve through a push rod amd the rocker arm.
Camshaft of an Engine incorporating a Rocker Arm

5. As the cylinder cam profile rotates the follower moves upwards
As the cylinder cam profile rotates the follower moves upwards. When the follower reaches the top, the cylinder cam rotates in the opposite direction and follower moves back down.
(The Cylindrical Cam )
Barrel Cam
These cams are normally composed of a cylinder which has a groove cut out of its surface and it is in that the follower runs up and down. This type of cam can be seen in some old clock mechanisms.

6. Different Types of Cam and Follower Systems
(Plate Cam)
Roller follower
Flat follower
Knife edge follower
(Cylindrical Cam)
End Face Cam
Barrel Cam

7. Types of Cam (Plate Cam) (Face cam) (Barrel Cam) (Cylindrical Cam)