It means "what are you here for?", though properly written it would be: "¿A qué vienes?", in Spanish questions also carry an opening question Mark, and question words "que", "cual", "donde" (what, which, where, etc) are accented when in the question, but usually not accented when part of an ordinary sentence that is not a question. I hope I have answered your question. Regards, Jaime

It practically means " what are you doing here?"