Answer
domain: $(-\infty, +\infty)$
range: $\left\{-2\right\}$
The relation is a function.
Work Step by Step
Recall:
(1) The domain of a function is the set of all its first coordinates.
(2) The range of a function is the set of all its second coordinates.
(3) The Vertical Line Tests states that if every vertical line will pass through the graph of a relation in at most one point, then the relation is a function.
Note that every vertical line will pass through the given graph at exactly one point only.
Thus, the given graph represents a function.
The given function has:
domain: $(-\infty, +\infty)$
range: $\left\{-2\right\}$
