The range of a function is the set of the all values taken by the function, for all possible inputs.
When you watch this from a graphical point of view, the range is the portion of the y axis that the graph spans.
In this case, you can see that the lowest point reached by the function (its minimum) is [tex](3,-2)[/tex]. You can also see that the function is unbounded upwards.
So, the range is [tex][2,\infty)[/tex], and the lowest value is thus 2.
