comprises a printed circuit board
that connects several connectors
in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors.
It is used as a backbone to connect several printed circuit board cards together to make up a complete computer system
One popular early computer system that used this approach was called the S-100 bus
because the connectors used had one hundred pins.
Some computers like the Apple II and the IBM PC
integrated an internal backplane for expansion cards.