A conceptual model is a representation of your hypotheses and the domain of your research. It specifies the units of analysis, the time and geographical location of your population the variables (concepts that vary), and the effects or correlations between the variables. The most common error in conceptual models is the difference between a mediator and a moderator. A mediator is a variable that is influenced by the independent variable and, in turn, affects the dependent variable. This is also called an indirect effect of the independent variable on the dependent variable. An effect can be mediated partially, when there is a direct effect of the independent on the dependent variable besides the mediation. A moderator is a variable that changes the effect of the independent variable on the dependent variable. It affects the direct effect and not another variable, so it is usually drawn as an arc pointing at the center of another arc or as an arc with two tails, one starting from the independent variable and the other from the moderator.
Two ways of visualizing a moderated effect