General Discussion

maybe some jurisdictions make a distinction, and perhaps the age of the victim factors into sentencing, but for the most part, under age is under age.

if you're a psychologist studying or treating patients, these are useful distinctions. the younger victim, the more outrageous the offense and the psychology can be quite different. there's clearly something very, very wrong with sex with a child who hasn't even reached puberty. such a person is clearly getting their own gratification at the expense of an child who can't possibly have any concept of what's going on. the older the victim gets, the more it is a matter of where society has decided to draw the line. chronological age is a bit arbitrary in determining when someone really can understand the concept of giving consent, but it's the best we can realistically use. so the psychology may be just as insensitive to the victim as with a younger child, or it may be that they are trying to have an actual relationship with the victim (and it may appear to be reciprocal), but they may not understand or accept society's rules and laws and have trouble abiding by them.

to be clear, it's *always* immoral when for an adult to have sex with a minor, but the levels of moral outrage vary depending on the circumstances and the relative ages and circumstances, and these distinctions may be helpful in distinguishing these.

but yeah, at a high level, it is splitting hairs. that's why lay people just call all these things "pedophilia" rather than get into the perhaps subtle differences.