Pinout Part of the Chips and soldering and wire and stuff is used to connect a game board to a cabinet. Generally this is an edge connector on one side of the game board. It normally consists of one or two set's of connectors, but it will vary. Each pin on the connector is used to send a particular type of info between board and cabinet. This will include, but isn't limited to, joystick movement, power, video out, fire buttons and the like.
Different boards have different configurations of pins, just because people like to be awkward.
The configuration of pins for a specific board is referred to as the Pinout. A little turny spinny thing which in technical terms controls the flow of current through a circuit. In realworldspeak, a volume control or other adjustable thing. They're important though, and the name suggest that they act to control capacity somehow. There's also a different type that looks like a nut coloured smartie, it's still a capacitor thing though.