We always used to say "population" to mean the whole count of people in a country. Yeh, for example the population of Singapore is in the range of 5 to 6 millions.
Cool, what happens in statistics that we also call the whole count or entire amount of things under study as a "population".
Example: a company that produces pens, here: the whole amount of products "pens" that was produced, and to be produced in future is considered as our "population".
You see? yep a "population" is usually a large count/amount of items. It could be infinite as well.
So, can you think of several examples as "populations" ?