The "m" in y = mx + b is the <u>slope.</u>
It is the number of units a point goes up, down, left, or right each time. Making the line linear/straight.
"rise" is the the number of units you go up(+) or down(-), "run" is the number of units you go to the right
For example, if your slope is:
You are going up 1 unit, and to the right 2 units
3 or
You are going up 3 units, and to the right 1 unit
You are going down one unit, and to the right 2 units
-3 or
You are going down 3 units, and to the right 1 unit