Hi,
In-text means output which will be copied and pasted into the body of another report.
Post-text means output which will be appended to a document.
Slight differences in where titles/footnotes should be placed and occasionally fonts. Otherwise they are pretty much the same.
POP - well writing it like that indicates something to do with an email account/system? I think you mean populations? If so then they are groups who fulfull certain criteria to be analysed on. So a male population would be anyone of the whole study with gender male.