They can tell if your hymen is broken.
If you're 16 or over they will ask you if you want your parents to know.
You have the choice of whether to say yes or no
There is no way for them to tell (though there is a way for them to tell if you have had a child... your body is never quite the same). Also, I'm not sure where you live, but HIPPA may protect you, and I also believe you have the right to request to be seen without your parents (depending on your age): link
the doctor (gynecologist) tell that a girl has a tear in her hymen, no hymen or just fragments of a hymen, but (unless the sperm still is present of course) NO doctor, NO PERSON can know how that happened , (at 6 when jumping, at 12 when horse riding or dancing ballet or at 14 from tampons or fingering or at 18 from having sex with 6 guys in a row. LOL)
Just the girl and her first sexual boyfriend can know it.
The doctor can know if there was a childbirth of course.
btw, if there's no trace of abuse the doctor is NOT interested to know it , unless he needs it for his diagnostic of course, to exclude the possibility of a STD for instance. Above a certain age the doctor will have to respect confidentiality.
(probably above 16 yrs)
There are many kinds of hymen. Look at some drawings : link