A Correlation is an estimate of how related two variables/traits are. The scale runs from zero to one, where zero indicates a complete lack of a relationship and one indicates a perfect relationship. Anything over 0.5 is considered a good correlation between traits

Example of a correlation of 0: There is a correlation of zero between an adults shoe size and their IQ/SAT score

Example of a correlation of 1: There is a correlation close to one between an adults shoe size and foot size