Explanation:
gradient = slope. or similar names.
it expresses the "steepness" of the line. how strongly is it going up or down or ... at all ?
it is represented by the ratio
(y coordinate difference / x coordinate difference)
when going from one point on the line to another.
for these 2 points we see (when going from the first to the second)
x changes by +1 (from -1 to 0).
y changes by -6 (from 2 to -4).
so the slope or gradient is
-6/+1 = -6