Answer
(refer to the step by step part for the explanation)
$\\$The graph of $y=b$ is a line whose points all have a y-value of b. All these points belong to a horizontal line.
Work Step by Step
$y=b$ can be written as $y=0x+b$.
$\\$This means that for whatever value of x, the value of y is always going to be b.
$\\\\$Thus, the points $(−1,b),(0,b), \text{ and } (1,b)$ are all in the graph of $y=b$.
$\\\\$Connecting the points together to graph the line forms a horizontal line.
$\\\\$Therefore in general, the graphs of equations of the form $y=b$, where b is any real number, are horizontal lines.