You can hide files in a view by applying a mask or a filter. In both cases, you use one or more rules to specify which files should be hidden.
When you use a mask, hidden files are not shown, but still take up space in the view. A mask is always applied to an existing view. You can apply a mask from the view's Display panel.
When you use a filter, hidden files are entirely omitted from the view. A filter always creates a new view. You apply a filter using the Filter... command from the "Window" menu.