How do population genetics people define a population? How do population genetics people define a population? 

Do they define it as a layman will do? say Africans, Americans, or so? Or is there a more scientific way of doing so? For example, I think defining one's population as one's allele frequencies makes more sense, but has this point been discussed previously?
A population is defined as a group of people (or organisms of the same species) living together in a geographical region. However, for human genetic studies, it is wise to use ethnicity as well (so group of people with the same ethnic background). See here how they define population in the 1000 genomes project.