PCI Express as a high-bandwidth, low pin count, serial, interconnect technology.
It was designed to replace the older PCI and AGPbus standards.
PCIe has numerous improvements over the older 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 (Advanced Error Reporting, AER), and native hot-swap functionality.
PCI Express architecture provides a high performance I/O infrastructure for Desktop Platforms with transfer rates starting at 2.5 Giga transfers per second over a x1 PCI Express lane for Gigabit Ethernet, TV Tuners, Firewire 1394a/b controllers, and general purpose I/O.
PCI Express architecture provides a high performance graphics infrastructure for Desktop Platforms doubling the capability of existing AGP8x designs with transfer rates of 4.0 Gigabytes per second over a x16 PCI Express lane for graphics controllers.
A lane is composed of two differential signaling pairs, with one pair for receiving data and the other for transmitting.
Express Card utilizing PCI Express interface, developed by the PCMCIA group for mobile computers.
PCI Express Advanced Power Management features help to extend platform battery life and to enable users to work anywhere, without an AC power source.
The PCI Express electrical interface is also used in some computer storage interfaces SATA Express and M.2.
The broad adoption of PCI Express in the mobile, enterprise and communication segments enables convergence through the re-use of a common interconnect technology.
PCI-E is a serial bus which uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction [one transmit, and one receive pair].
PCI Express supports 1x [2.5Gbps], 2x, 4x, 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs].