It roughly means "nowhere worth mentioning" / "practically nowhere".

Not really = not much/no/ very few/hardly

Not really, means no but when someone uses "not really" it means there is a small part that might be yes. For example, maybe she has not visited any places yet, but she did go out of her apartment for a few minutes or hours, but did nothing special so this might be why she might say "not really." example, I could also say "Not really. I spent most of yesterday getting settled in my apartment. I only went to the nearby grocery store for a few minutes to get dinner." So "not really" is a passive way of saying No, but No may be too straightforward and not fully true so you say, "Not really".

Thanks sir and ma'am