A shared channel that transmits data one bit after the other over a single wire or fiber; for example, Ethernet uses a serial bus architecture. The I/O bus from the CPU to the peripherals is a parallel bus (16, 32 or 64 wires, etc.).

Serial Bus Vs. Serial Port
Although sounding similar, a serial bus differs from a serial port. Both use serial transmission; however, the serial port connects the computer to one device, whereas a serial bus allows for the connection of multiple devices. See bus and PCI.