folic acid is a form of the vitamin B9. Vitamin B9 (Folic acid and Folate inclusive) is essential to numerous bodily functions and it is especially important during periods of rapid cell division and growth as it can reduce the risk of neural tube defects such as spina bifida by about 70%.(The neural tube is a structure in the baby that develops into the brain, spinal cord, and other parts of the nervous system).
Prenatal vitamins are a source of supplemental vitamins and minerals that are usually deficient during pregnancy since the baby requires a lot of these for healthy development.
Ideally, a woman expecting to or becoming pregnant would get all this from her daily diet but we all know how hard it is to eat everything that's recommended within the day so most doctors will recommend both folic acid and prenatal vitamins a month before, during and a month after the pregnancy. If taking both causes symptoms such as nausea you may try to reduce the amount of folic acid you are taking as I believe the prenatal vitamins will usually contain some.

I may be pregnant, but I dontk now yet. Should I take the prenatal anyways? What If I end up not being pregnant, do I just stop taking them? will it hurt me at all to take them without knowing for sure?

If you can take them it would definately be good in the case that you are pregnant. They're sort of like a multivitamin but with higher concentrations of those vitamins and minerals than you would need extra of during pregnancy so they won't hurt you at all if you're not pregnant. Yes you would just stop taking them if it turns out you're not just like you would a multivitamin. Good job on the thinking ahead!

they won't affect the pregnancy test (just saw your question)and Congrats if you are!