A HID collection is a meaningful grouping of HID controls and their respective HID usages.
Controls should be grouped together if they are logically related or are functionally dependent on one another. For instance, a SHIFT key and a letter key on a keyboard should not belong to separate collections. Collections can have nested subcollections, also referred to as link collections. Report descriptors define one or more top-level collections, and the report items, associated with each collection, define one or more HID reports.
Windows extends the concept of a HID collection to include the following: