PCI Express (Peripheral Component Interconnect Express)
PCI Express (Peripheral Component Interconnect Express) is a computer expansion bus standard designed to replace the older PCI, PCI-X, and AGP bus standards. PCIe has numerous improvements over the aforementioned bus standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance-scaling for bus devices, a more detailed error detection and reporting mechanism, and native hot-plug functionality. More recent revisions of the PCIe standard support hardware I/O virtualization.
Source: wikipedia