Two terms that are frequently confused are moderation and mediation:
Definitions of moderating and mediating:
A mediating variable is one that accounts for or alters another relationship. A strict definition is that the mediating variable has to greatly reduce or even eliminate the relationship. A more lenient definition is that it affects the relationship. I favor that more lenient definition. A moderating variable is one that interacts with a variable. An interaction means that the relationship between one independent variable (IV) and the dependent variable (DV) is different at different levels of the other IV. Read more!