The word population has a number of distinct but closely related meanings in statistics.
1. A finite and actually existing group of objects which, although possibly large, can be enumerated in theory (e.g., people living in the United States).
2. A generalization from experience which is indefinitely large (e.g., the total number of throws that might conceivably by made in unlimited time with a particular pair of dice). Any actual set of throws can then be regarded as a sample drawn from this practically infinite population.
3. A purely hypothetically population which can be completely described mathematically.