What is PCIS?

It's likely you meant "PCIe" (Peripheral Component Interconnect Express) or possibly "PCI" (Peripheral Component Interconnect). Since both are very similar, I'll explain them together, highlighting their main differences. Both are interface standards used to connect hardware components within a computer, such as graphics cards, sound cards, network cards, and storage devices, to the motherboard. PCIe is the successor to PCI and offers significantly improved bandwidth and performance compared to PCI. PCI uses a parallel bus, while PCIe uses a serial bus, which allows for faster data transfer rates and more efficient communication. PCIe is the dominant standard today due to its superior performance and scalability. If the technology you wanted to know about wasn't PCI or PCIe, please clarify.