Explanation:
The y axis is vertical. Anything perpendicular to this is horizontal.
All horizontal linear equations are of the form y = k, where k is any number.
In this case, k = 5 so that the line y = 5 goes through all points with y coordinate 5. Two points on this line are (-4,5) and (1,5).
Note how y = 5 is equivalent to y = 0x+5. We see the slope is 0 and the y intercept is 5. Compare this to y = mx+b.