Hey,
This should be just old blood clotted in your vagina, and so doesn't look fresh anymore and gets out of you in that "brown stuff" form. It comes before your period. This is common if you have never had a period. the blood is real brown and almost looks like diarrhea it is just very old uterus lining that has been waiting for you to hit puberty so it can be shed. Congratulations girls you are a woman now.
But, if this continues almost everyday for weeks, tell your mom. I'm sure your mom would be happy to offer you women advice and knowledge so you don't panic like this. Don't risk it.
I hope this helps. HAHA
XP
Oh, and, a bit more info
You should have the brown stuff in your drawers checked out by your doctor only if it is accompanied by a foul or fishy odor. In that case, it could be an irregular discharge or sign of infection.
See a gynecologist then :P