Describing Domain and Range

The domain of a function is the set of all possible $x$-values. The range is the set of all possible $y$-values. Notice that, horizontally, our graph spans from $x=0$ to $x=6,$ inclusive. These values are the lower and upper boundaries of our domain. $$\begin{array}{c}D\text{: }0\le x\le 6\end{array}$$ Meanwhile, vertically, our graph spans from $y=\text{-}1$ to $y=2,$ inclusive. These values are the lower and upper boundaries of our range. $$\begin{array}{c}R\text{: }\text{-}1\le y\le 2\end{array}$$