ItemAttributes objects are used to describe attributes of items to query for when using the document.getItems(attributes) function. It serves as a description of a filter applied to the queried items, defined by various fields that can either be set to true, false, or null.
Sample code:
// All selected paths and rasters contained in the document.
var selectedItems = document.getItems({
type: [Path, Raster],
selected: true
});
// All visible Paths contained in the document.
var visibleItems = document.getItems({
type: Path,
hidden: false
});