Motherboard provides the connectivity to peripherals to the CPU like our nervous system. There are two main bridges on motherboard which connect the various components including the processor.

North Bridge
North bridge is connected to the memory bus, front side bus (FSB), and AGP bus. Memory bus is further connected to the memory, front side bus is connected to the CPU or processor and AGP bus is further connected to the graphic card.

South bridge
South bridge is connected to the ATA bus and the PCI bus. ATA bus is further connected to the disk drives providing a path between the motherboard and the disk drives including Compact disk drive (CD-drive) and Hard disk drive. PCI bus is connected to the PCI-based hardware devices and thus providing the only path between the PCI devices and the motherboard.