1-This is the period when people eat out.
Does this mean that all the people eat out all the time or could it be used when a lot of people often eat out?
It could be only some people. The meaning is that those people who do eat out, do it during this period.
Thanks a lot mykwyner,
I think the negative sentence:
2-This is the period when people don't eat out.
literally means that nobody eats out, but it is used to mean "very few people eat out". Am I correct?