I have seen a strange phrase "flight time is compensation" in a few questions and answers here, mostly related to what PPL can do for free and what is not allowed.

This looks so confusing that I ask a question. If the private pilot cannot get the compensation, and flight time **is** a compensation, how could such pilot legally fly? One should theoretically get CPL before having the possibility to log any flight time.

This is surely not the case, I understand. When the "flight time is compensation" and when it probably is not?

Most of the confusing questions are related to USA (so FAA).