A PCI ECP Parallel Port driver is software that allows the operating system to communicate with a parallel port device connected via a PCI (Peripheral Component Interconnect) card, specifically in the ECP (Extended Capabilities Port) mode. ECP is a mode used for high-speed data transfer over the parallel port, primarily for printers or other peripherals. While this technology was popular in the past, it has become less common with newer devices relying on USB or network-based connections.