Description: The word 'slot' is used to refer to bus slots. The last case (motherboard) refers to situations where a functional element is integrated onto, say, a motherboard and connects to a bus without a connector. It still takes up an expansion site on the bus but this is termed a 'virtual slot' as opposed to a physical slot (see the attribute 'Virtual Slot'). Virtual slots are in effect permanently occupied expansion sites. This attribute establishes which category of physical slot this table entry is defining.