This is a bacterium Chlamydia trachomatis. It is the most common STI and young people are, for unknown reasons, especially at risk.
What are the symptoms?
This is a difficult one. Often symptoms don't show at all and this is why it can be potentially very damaging. It is usually only found by specific screening at a sexual health (GUM) clinic. If there are any symptoms they will be a vaginal discharge, pain in the pelvic area during sex or, as with men, pain when urinating.
Is there treatment available and what is it?
Yes - through antibiotics
Are there long term effects?
Not if it is caught early enough. However it can cause infertility if not caught in time - and, if passed on from a mother to her baby, the effects can be terrible.
When and if you're ready:
You really must say you're a virgin the first time you have sex.
Go really slowly and gently, don't have overly high expectations - Meantime, enjoy your virginity and maybe explore