Domain: the minimum and maximum x values
Range: the minimum and maximum y values
Graph 1:
The arrows on the ends of the line indicate that it continues on in both directions infinitely. Because it has a slope (the exact value of which is irrelevant), it continues left and up, and right and down infinitely. Thus, the domain and range would both be infinity.
Graph 2:
There are dots at both ends of the line, indicating that the graph is not infinite but limited. The furthest negative x value is the minimum for the domain, and the furthest positive x value is the maximum for the domain. Because the dots are filled in, they are definitely on the graph, so you use brackets to express it. [-1,5].
For the range, the same is true but now looking at the y-values. [-1,2].
If the dots had been open and not filled in, parenthesis would be used to show that those values aren't part of the graph but that's where it stops. Brackets show that the graph definitely ends at exactly that point.
