So in one case (GPA and SAT) we have a positive correlation and the other example (GPA and Height) we have zero correlation. What about the values? We haven't calculated them yet - I just ballparked them.

Let's look at GPA and amount of drinking (we survey students and measure the number of drinks per day vs. GPA - these are made-up data.) The more you drink, the worse your GPA. This is a negative correlation.

Big Idea:
You get a tight, elongated elipse such as this scattergram and you have a good predictive relationship and correlation!