The scales were weird. So Karl Pearson came up with the idea of first transforming each score to a standard score. The full name for r is the Pearson Product Moment Correlation Coefficient. So product moment means multiply the deviations This is laborious to convert to z scores, so there are many other algebraiclly equivalent formulae that are easier to do. So as height increases, weight increases a little.
Correlation is low because there are some short fat people and some tall skinny people.
Of course not. That's very high. But can't draw cause and effect conclusions. However, even if you don't know the cause and effect relationship, if two variables are related, they can be used to make predictions . That is, put the x scores on the abscissa, y on ordinate.