Correlation is a simple measure of how two variables are related.
If correlation is greater than 0, then the variables are described as positively related or directly related. If correlation is less than 0, then the variables are described as negatively related or inversely related. Income is positively correlated with education. Nonlinear relationships may not be reflected in correlations, so it always a good idea to plot the variables that you describe with a correlation. Note that correlation only permits you to make an empirical statement about how two variables are related.