Answer
$f(x)=\left\{\begin{array}{l}
-1\ ~~~\mathrm{i}\mathrm{f}~~\mathrm{x}\ \leq 0\\
1\ ~~~~~~\mathrm{i}\mathrm{f}~~\mathrm{x}\ \gt 0
\end{array}\right.$
Domain: $(-\infty,\infty)$
Range: $\{-1,\ 1\}$
Work Step by Step
We see that the graph consists of two horizontal lines, $y=-1$ and $y=1$. Solid circles indicate that the value belongs to that piece of the function (e.g. "$\leq$" or "$\geq$"), while open circles indicate that the value does not (e.g. "$\lt$" or "$\gt$"). Thus we have:
$f(x)=\left\{\begin{array}{l}
-1\ ~~~\mathrm{i}\mathrm{f}~~\mathrm{x}\ \leq 0\\
1\ ~~~~~~\mathrm{i}\mathrm{f}~~\mathrm{x}\ \gt 0
\end{array}\right.$
We see that the domain is all real numbers, while the range is either 1 or -1:
Domain: $(-\infty,\infty)$
Range: $\{-1,\ 1\}$