Note that chapter 1 of the textbook on epidemiogy is about causality.

Hence, as has long been recognized in epidemiology, there is a need to develop a more refined conceptual model that can serve as a starting point in discuions of causation. In particular, such a model should addre problems of multifactorial causation, confounding, interdependence of effects, direct and indirect effects, levels of causation, and systems or webs of causation.

This chapter covers the "sufficient-cause model." Later chapters cover the potential-outcome or counterfactual model.

Effect of a factor

is a change in a population characteristic that is caused by the factor being at one level versus in another (but what does this mean?)

exposures

potential causal characteristics (which is why diabetes could be called an exposure.

Each person in a cohort of smokers could potentially receive anti-smoking literature in the mail. If the mailing is done, the incidence of lung cancer in 5 years is one value and if the mailing is not done it is another value. The two exposures represent "alternative histories" and the two different incidence rate values are potential outcomes. The difference in rates or the ratio of rates are the causal rate difference or causal rate ratio.