Headers are created when you place a dimension or discrete field on the Rows shelf or the Columns shelves. The headers show the member names of each field on the shelves. For example, in the view below the column headers show the members of the Order Date field and the row headers show the members of the Category field.
You can show and hide row and column headers at anytime.
To hide headers:
Right-click the headers in the view and select Show
Select the field in the view whose headers you want to
show and select Show Header on the field