What Does the QueryString Method Do? Documentation for it?

I looked in the Kentico documentation for information on what this method does, but I was unable to find it when I did a search through the Kentico documentation, I don't see this method listed at all. I am mostly wondering what the @parameter@ does in this context:Let's say that this method is implemented as follows inside a transformation:QueryString[@parameter@],false)it seems like a lot of these methods are either not in the documentation, or the documentation search feature isn't working.EDIT: this is on the portal engine not MVC