First, many buses have slots into which connectors are plugged. This is electrically identical to wall receptacles in your house where you plug in electrical appliances so they can get the juice to operate. Actually, a better analogy might be the telephone plug in the wall. Any telephone receiver may be plugged into different houses and it will respond although it acquires a different address, or phone number, when it is moved to a different place. In a similar way inside a computer, the slots have addresses to which they respond.