[raistlin]

well i might be wrong but as far as i understand

tgirl is short for transgendered girl so that is quite a wide spectrum and I guess could cover anyone who classes their own gender as female, transitioned or not.

shemale is most commonly used to describe a pre-op transsexual. Someone who has permentantly transitioned to a female but still is in possession of some of their male genetalia

pre-op & post op are used to describe people who have/have not undergone SRS - Sex Reassignment Surgery which is ofc surgery to change the genetalia

As for dating I saw there was a sticky topic in the dating section with a lot of information regarding this