The domain is the set of available values of x on which a function y(x) can be evaluated.
The range is the set of values of the function y(x), calculated for the values of x of the domain.
Based on the previoues definitions, you can notice that the domain and range of the graph are the following:
domain y: (-∞,4]
range y: [-5,2]
The first interval opens with minus infinite because in the graph tou can observe that an arrow points to the left.