currentmember referred to in WHERE Clause

Hi All,The following is mdx selecting from a subselect . any idea what is the purpose of having a WHERE clause i.e WHERE [Date].[Calendar].CurrentMember . What is it's purpose ? What is currentmember is referring to. I can't see what it is trying to enforce. SELECT NON EMPTY { [Measures].[Sales Amount] } ON 1,NON EMPTY { ([Product].[Category].[Category].MEMBERS ) } on 2 FROM ( SELECT ( { [Date].[Calendar].Members]} ON 0 FROM [Adventure Works]) WHERE [Date].[Calendar].CurrentMember )) this is the sort of boiler plate mdx generated out by SSRS when using a parameter