This compensated for number of cases, but not for size of the raw score scale. The scales were weird. So Karl Pearson came up with the idea of first transforming each score to a standard score. 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. You can use the keyword WITH and spss will produce an asymmetric matrix of variables in the first list correlated with variables in the second list. TO GPA will produce two different matrices. If so, one asterisk will appear for .05 and two for .01. SIG prints number of cases and significance level.