Peter N. answered 04/01/19
PhD with over 15 years of teaching social science statistics.
A population contains all members of a specified group (the entire list of possible data values) such as all women on Earth, or all United States citizens. They key word is "all", meaning every possible member of the group.
A sample is a part, or a subset, of a population. The size of a sample is always less than the size of the population that it is drawn from.