If we want to go from A to C via B, we have to go horizontally, then vertically.
Next,
If we want to go from C to E via D, we again, have to go horizontally, then vertically.
This gives us the rate of change of the line ACE.
This horizontal movement is the run and ths vertical movement is called the rise.
If we take the ratio of Rise/Run, we have slope.
Answer: SLOPE