Hello! That's vaginal discharge, it's normal and nothing to worry about. But if you get yellow/green type of discharge and it's itchy then it could be a yeast infection which the doctor will put you on some type medication and it can also be purchased at a drug store w/o a prescription. I haven't used any of those so I don't know which one to comment on sorry about that. Some yeast infections are caused by taking medications/antibiotics, sexual intercourse and taking a lot of bubble baths per week.. Hope that helps some.

if its in the down are that probably you know what and if its around then its probably from you boyfriend, husband. Idk

Probably ash or something.

Idk what it is, but it's totally normal.

Do you have any brothers? or has anyone been in your room ( male ) recently? Because that sounds like semen and that is very horrible. I would recommend washing those right away or throw them away. And talk to your family about it. If someone did ejaculate on your thong then they will stop if you bring it up. Best of luck!