This linkage reverses the motion put into it. The pivot or fulcrum is in the middle of the simple lever so the output travels the same distance as the input. This type of linkage is called a reverse motion linkage.

This linkage also reverses the input motion, but because the position of the pivot has changed on the simple lever, the input motion is small and the output motion is much larger. This is also a reverse motion linkage

This is a bell crank. It changes the direction of motion but does not reverse it. By moving the pivot input and output distances can be changed.

These are used when objects are required to move in a straight line at a set distance apart. A folding toolbox or a folding pram would be examples of this kind of linkage system.

Push pull linkages produce input and output motion in the same direction. By moving the fixed pivots the size of motion can be changed.