Both correlations (+.71 and +.30) are positive correlations, meaning that as one variable increases, the other variable also increases. In the case of the twins, the first variable is the IQ of one of the twins and the other variable is the IQ of the second of the twins. This means that if one of the twins has a high IQ, the other also seems to have a high IQ. The same would be true of low IQ scores (if one is low, the other is also low). For the case of income, a positive correlation means that as family income increases, so do the IQ scores of the children. Note that +.71 is a much stronger correlation than +.30, which means that the scores for the correlation of +.71 would tend to be closer than the scores for the correlation of +.30.