PCIe16 stands for PCI-Express x16. It is primarily used for video cards in a desktop PC
PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common motherboard interface for personal computers' graphics cards, hard disk drive host adapters, SSDs, Wi-Fi and Ethernet hardware connections. 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. More recent revisions of the PCIe standard provide hardware support for I/O virtualization.
Defined by its number of lanes, (the number of simultaneous sending and receiving lines of data as in a highway which features traffic in both directions) the PCI Express electrical interface is also used in a variety of other standards, most notably the laptop expansion card interface ExpressCard and computer storage interfaces SATA Express, U.2 (SFF-8639) and M.2.
Format specifications are maintained and developed by the PCI-SIG (PCI Special Interest Group), a group of more than 900 companies that also maintain the conventional PCI specifications.