The term PCI Function refers to a device or component on a computer's motherboard that is connected via the PCI (Peripheral Component Interconnect) bus or the newer PCIe (PCI Express) standard. These functions are typically associated with various hardware components like network adapters, sound cards, graphics cards, storage controllers, and other peripherals.

In the context of a Windows driver, a PCI Function driver is the software that allows Windows to recognize and properly communicate with a PCI-based device, allowing it to function correctly. If you're seeing a PCI Function in your Device Manager under "Other devices" or with an exclamation mark (indicating a missing or problematic driver), it generally means that a device connected via PCI/PCIe hasn't had its driver properly installed or recognized by the operating system.