A aughterboard or daughtercard is a circuit board meant to be an extension or "daughter" of a motherboard (or 'mainboard'), or occasionally another card. In particular, daughterboards often have plugs, sockets, pins, connectors, or other attachments for other boards, which is what differentiates them from a standard expansion board such as for PCI or ISA. In addition, daughterboards usually have only internal connections within a computer or other electronic device rather than any external ones, and usually access the motherboard directly rather than through a computer bus.