Answer
The variable $h$ in the equation $y = \sin (x - h)$ determines the horizontal (phase) shift of the graph.
$y = \sin (x - 0)$ -> no phase shift
$y = \sin (x - (-\frac{\pi}{4}))$ -> $\frac{\pi}{4}$ or $45^{\circ}$ phase shift to the left
$y = \sin (x - (-\frac{\pi}{2}))$ -> $\frac{\pi}{2}$ or $90^{\circ}$ phase shift to the left
Work Step by Step
See below graph for reference:
