When you are asking a question on Wikianswers using the ask box at the top, potential duplicate questions to yours will be shown underneath the box.
The aim is to help askers find questions that have already been asked, and hopefully answered, and to prevent duplicated questions.
The tool ignores very common words ("noise words").
As an example, if you type in "river nile", you should see the following questions appear. You can either choose to continue typing your question, or click one of the options to visit that question instead.