So things must be balanced. There are many. In most cases a bus is something that connects more than two devices or chips. Peripheral busses allow one device to talk to other devices. Peripheral daisy chains work in much the same way.
Every device is supposed to have an in and an out port.
They all have their own timings and data widths. You'd have to read the technical notes to know for sure, so this not usually mentioned, so you'd have to be a real propeller-head to care. Internal Bus is how chips on the motherboard talk to each other. So often your CPU can way out-speed the main bus. So there are many busses in your computer, and often inside a single chip.