Mathematica Stack Exchange is for users of the software Mathematica developed by Wolfram Research, as well as related products like gridMathematica, Wolfram Workbench, Player (Pro), and the CDF Player.
EDIT: and https://mathematica.stackexchange.com/tour says
Mathematica® Stack Exchange is a question and answer site for users of Wolfram Mathematica and the Wolfram Language.
What's your Mathematica question? Be specific. Is your question about Mathematica?
EDIT: screenshot http://i.imgur.com/EDWWOUk.png