Notice how the arrows on the mapping diagrams are paired with the points on the graph of the functions.
You can move the point for $x$ on the mapping diagram to see how the function value for the function $ f(x) = \sin(\frac {\pi}2 x)$ changes both on the diagram and on the graph.
The arrow on the point on the mapping diagram target axis indicates whether the value of the function $f(x)$ is increasing (pointing up) or decreasing (pointing down).

Notice how the graph and mapping diagram visualize the fact that for the sine function, if $B>1$ then  $\sin(Bx)$  has the same basic shape as $\sin(x)$ though it happens more "quickly".
See Subsection TRIG.LCOMP

Check the box to show points on the graph and arrows on the diagram for the function $ f(x) = \sin(\frac {\pi}2 x)$.
Move the slider to change the function to $\cos$ or $\tan$.