The<unk>  of disease given an exposure is simply the rate of disease (incidence) in the exposed people minus the rate in the unexposed people.
So the<unk>  for lung cancer in smokers is, in essence, simply the rate of lung cancer amongst smokers minus the rate of lung cancer amongst non-smokers.
The population<unk>  is an estimate of the proportion of disease or other outcomes in a community due to exposure to a specific factor.
For example, Tobacco smoking is the main cause of lung cancer, but a small proportion of cases of lung cancer in almost all communities are due to other exposures, for example, radon, indoor air pollution, outdoor air pollution, arsenic, unfortunate genetics and so on.
It is possible to imagine what would happen in a community if, say, you removed all the radon, and left everything else unchanged. The number of lung cancer cases would fall. This fall is the population<unk>  for lung cancer from radon. Please note that this isn't actually possible, so this is a thought experiment, but for all that it's a useful one.
Attributable risk
Absolute deviation
Sample size
Absolute risk reduction
Ancillary statistic
Hazard ratio
Point prevalence
Number needed to treat