When you find the slope of a trend line in a scatterplot, you're figuring out how much one thing changes when another thing changes. Imagine you have a graph that shows how much you study and the grades you get.
If the trend line has a positive slope, it means that as you study more, your grades tend to go up. So the steepness of the line shows how much your grades increase for each extra hour of studying.
On the other hand, if the slope is negative, it means that as you study more, your grades go down, which would be pretty surprising but could happen in some cases!
If the slope is flat (close to zero), it means that studying more doesn't really change your grades much at all.
So, the slope helps us understand the relationship between the two things we're looking at in the scatterplot. It tells us if they go up, go down, or stay the same together!